diff --git a/src/bin_node/node_config_file.ml b/src/bin_node/node_config_file.ml
index daf854c81..ca35f30b4 100644
--- a/src/bin_node/node_config_file.ml
+++ b/src/bin_node/node_config_file.ml
@@ -206,61 +206,50 @@ let limit : P2p.limits Data_encoding.t =
        (merge_objs
           (obj10
              (dft "connection-timeout"
-                (Data_encoding.describe
-                   ~description: "Delay acceptable when initiating a \
-                                  connection to a new peer, in seconds."
-                   float) default_p2p_limits.authentication_timeout)
+                ~description: "Delay acceptable when initiating a \
+                               connection to a new peer, in seconds."
+                float default_p2p_limits.authentication_timeout)
              (dft "authentication-timeout"
-                (Data_encoding.describe
-                   ~description: "Delay granted to a peer to perform authentication, \
-                                  in seconds."
-                   float) default_p2p_limits.authentication_timeout)
+                ~description: "Delay granted to a peer to perform authentication, \
+                               in seconds."
+                float default_p2p_limits.authentication_timeout)
              (dft "min-connections"
-                (Data_encoding.describe
-                   ~description: "Strict minimum number of connections (triggers an \
-                                  urgent maintenance)."
-                   uint16)
+                ~description: "Strict minimum number of connections (triggers an \
+                               urgent maintenance)."
+                uint16
                 default_p2p_limits.min_connections)
              (dft "expected-connections"
-                (Data_encoding.describe
-                   ~description: "Targeted number of connections to reach when \
-                                  bootstraping / maintaining."
-                   uint16)
+                ~description: "Targeted number of connections to reach when \
+                               bootstraping / maintaining."
+                uint16
                 default_p2p_limits.expected_connections)
              (dft "max-connections"
-                (Data_encoding.describe
-                   ~description: "Maximum number of connections (exceeding peers are \
-                                  disconnected)."
-                   uint16)
+                ~description: "Maximum number of connections (exceeding peers are \
+                               disconnected)."
+                uint16
                 default_p2p_limits.max_connections)
              (dft "backlog"
-                (Data_encoding.describe
-                   ~description: "Number above which pending incoming connections are \
-                                  immediately rejected."
-                   uint8)
+                ~description: "Number above which pending incoming connections are \
+                               immediately rejected."
+                uint8
                 default_p2p_limits.backlog)
              (dft "max-incoming-connections"
-                (Data_encoding.describe
-                   ~description: "Number above which pending incoming connections are \
-                                  immediately rejected."
-                   uint8)
+                ~description: "Number above which pending incoming connections are \
+                               immediately rejected."
+                uint8
                 default_p2p_limits.max_incoming_connections)
              (opt "max-download-speed"
-                (Data_encoding.describe
-                   ~description: "Max download speeds in KiB/s."
-                   int31))
+                ~description: "Max download speeds in KiB/s."
+                int31)
              (opt "max-upload-speed"
-                (Data_encoding.describe
-                   ~description: "Max upload speeds in KiB/s."
-
-                   int31))
+                ~description: "Max upload speeds in KiB/s."
+                int31)
              (dft "swap-linger" float default_p2p_limits.swap_linger))
           (obj10
              (opt "binary-chunks-size" uint8)
              (dft "read-buffer-size"
-                (Data_encoding.describe
-                   ~description: "Size of the buffer passed to read(2)."
-                   int31)
+                ~description: "Size of the buffer passed to read(2)."
+                int31
                 default_p2p_limits.read_buffer_size)
              (opt "read-queue-size" int31)
              (opt "write-queue-size" int31)
@@ -276,9 +265,8 @@ let limit : P2p.limits Data_encoding.t =
        (obj2
           (opt "max_known_peer_ids" (tup2 uint16 uint16))
           (dft "greylist-timeout"
-             (Data_encoding.describe
-                ~description: "GC delay for the greylists tables, in seconds."
-                int31) default_p2p_limits.greylist_timeout)
+             ~description: "GC delay for the greylists tables, in seconds."
+             int31 default_p2p_limits.greylist_timeout)
 
        ))
 
@@ -295,30 +283,26 @@ let p2p =
         listen_addr ; closed ; limits })
     (obj5
        (dft "expected-proof-of-work"
-          (Data_encoding.describe
-             ~description: "Floating point number between 0 and 256 that represents a \
-                            difficulty, 24 signifies for example that at least 24 leading \
-                            zeroes are expected in the hash."
-             float) default_p2p.expected_pow)
+          ~description: "Floating point number between 0 and 256 that represents a \
+                         difficulty, 24 signifies for example that at least 24 leading \
+                         zeroes are expected in the hash."
+          float default_p2p.expected_pow)
        (dft "bootstrap-peers"
-          (Data_encoding.describe
-             ~description: "List of hosts. Tezos can connect to both IPv6 and IPv4 hosts. \
-                            If the port is not specified, default port 9732 will be assumed."
-             (list string)) default_p2p.bootstrap_peers)
+          ~description: "List of hosts. Tezos can connect to both IPv6 and IPv4 hosts. \
+                         If the port is not specified, default port 9732 will be assumed."
+          (list string) default_p2p.bootstrap_peers)
        (opt "listen-addr"
-          (Data_encoding.describe ~description: "Host to listen to. If the port is not \
-                                                 specified, the default port 8732 will be \
-                                                 assumed."
-             string))
+          ~description: "Host to listen to. If the port is not \
+                         specified, the default port 8732 will be \
+                         assumed."
+          string)
        (dft "closed"
-          (Data_encoding.describe
-             ~description: "Specify if the network is closed or not. A closed network allows \
-                            only peers listed in 'bootstrap-peers'."
-             bool) false)
+          ~description: "Specify if the network is closed or not. A closed network allows \
+                         only peers listed in 'bootstrap-peers'."
+          bool false)
        (dft "limits"
-          (Data_encoding.describe
-             ~description: "Network limits"
-             limit) default_p2p_limits)
+          ~description: "Network limits"
+          limit default_p2p_limits)
     )
 
 let rpc : rpc Data_encoding.t =
@@ -338,28 +322,23 @@ let rpc : rpc Data_encoding.t =
        { listen_addr ; cors_origins ; cors_headers ; tls })
     (obj5
        (opt "listen-addr"
-          (Data_encoding.describe
-             ~description: "Host to listen to. If the port is not specified, \
-                            the default port 8732 will be assumed."
-             string))
+          ~description: "Host to listen to. If the port is not specified, \
+                         the default port 8732 will be assumed."
+          string)
        (dft "cors-origin"
-          (Data_encoding.describe
-             ~description: "Cross Origin Resource Sharing parameters, see \
-                            https://en.wikipedia.org/wiki/Cross-origin_resource_sharing."
-             (list string)) default_rpc.cors_origins)
+          ~description: "Cross Origin Resource Sharing parameters, see \
+                         https://en.wikipedia.org/wiki/Cross-origin_resource_sharing."
+          (list string) default_rpc.cors_origins)
        (dft "cors-headers"
-          (Data_encoding.describe
-             ~description: "Cross Origin Resource Sharing parameters, see \
-                            https://en.wikipedia.org/wiki/Cross-origin_resource_sharing."
-             (list string)) default_rpc.cors_headers)
+          ~description: "Cross Origin Resource Sharing parameters, see \
+                         https://en.wikipedia.org/wiki/Cross-origin_resource_sharing."
+          (list string) default_rpc.cors_headers)
        (opt "crt"
-          (Data_encoding.describe
-             ~description: "Certificate file (necessary when TLS is used)."
-             string))
+          ~description: "Certificate file (necessary when TLS is used)."
+          string)
        (opt "key"
-          (Data_encoding.describe
-             ~description: "Key file (necessary when TLS is used)."
-             string))
+          ~description: "Key file (necessary when TLS is used)."
+          string)
     )
 
 let level_encoding =
@@ -392,29 +371,25 @@ let log =
        { output ; default_level ; rules ; template })
     (obj4
        (dft "output"
-          (Data_encoding.describe
-             ~description: "Output for the logging function. Either 'stdout', \
-                            'stderr' or the name of a log file ."
-             Logging_unix.Output.encoding) default_log.output)
+          ~description: "Output for the logging function. Either 'stdout', \
+                         'stderr' or the name of a log file ."
+          Logging_unix.Output.encoding default_log.output)
        (dft "level"
-          (Data_encoding.describe
-             ~description: "Verbosity level: one of 'fatal', 'error', 'warn',\
-                            'notice', 'info', 'debug'."
-             level_encoding) default_log.default_level)
+          ~description: "Verbosity level: one of 'fatal', 'error', 'warn',\
+                         'notice', 'info', 'debug'."
+          level_encoding default_log.default_level)
        (opt "rules"
-          (Data_encoding.describe
-             ~description: "Fine-grained logging instructions. Same format as \
-                            described in `tezos-node run --help`, DEBUG section. \
-                            In the example below, sections 'p2p' and all sections \
-                            starting by 'client' will have their messages logged \
-                            up to the debug level, whereas the rest of log sections \
-                            will be logged up to the notice level."
-             string))
+          ~description: "Fine-grained logging instructions. Same format as \
+                         described in `tezos-node run --help`, DEBUG section. \
+                         In the example below, sections 'p2p' and all sections \
+                         starting by 'client' will have their messages logged \
+                         up to the debug level, whereas the rest of log sections \
+                         will be logged up to the notice level."
+          string)
        (dft "template"
-          (Data_encoding.describe
-             ~description: "Format for the log file, see \
-                            http://ocsigen.org/lwt/dev/api/Lwt_log_core#2_Logtemplates."
-             string) default_log.template)
+          ~description: "Format for the log file, see \
+                         http://ocsigen.org/lwt/dev/api/Lwt_log_core#2_Logtemplates."
+          string default_log.template)
     )
 
 
@@ -508,11 +483,10 @@ let chain_validator_limits_encoding =
     (merge_objs
        (obj1
           (dft "bootstrap_threshold"
-             (Data_encoding.describe
-                ~description:
-                  "Set the number of peers with whom a chain synchronization must \
-                   be completed to bootstrap the node."
-                uint8)
+             ~description:
+               "Set the number of peers with whom a chain synchronization must \
+                be completed to bootstrap the node."
+             uint8
              default_shell.chain_validator_limits.bootstrap_threshold))
        (worker_limits_encoding
           default_shell.chain_validator_limits.worker_limits.backlog_size
@@ -547,24 +521,19 @@ let encoding =
        { data_dir ; rpc ; p2p ; log ; shell })
     (obj5
        (dft "data-dir"
-          (Data_encoding.describe
-             ~description: "Location of the data dir on disk."
-             string) default_data_dir)
+          ~description: "Location of the data dir on disk."
+          string default_data_dir)
        (dft "rpc"
-          (Data_encoding.describe
-             ~description: "Configuration of rpc parameters"
-             rpc) default_rpc)
+          ~description: "Configuration of rpc parameters"
+          rpc default_rpc)
        (req "p2p"
-          (Data_encoding.describe
-             ~description: "Configuration of network parameters" p2p))
+          ~description: "Configuration of network parameters" p2p)
        (dft "log"
-          (Data_encoding.describe
-             ~description: "Configuration of network parameters"
-             log) default_log)
+          ~description: "Configuration of network parameters"
+          log default_log)
        (dft "shell"
-          (Data_encoding.describe
-             ~description: "Configuration of network parameters"
-             shell) default_shell))
+          ~description: "Configuration of network parameters"
+          shell default_shell))
 
 let read fp =
   if Sys.file_exists fp then begin
diff --git a/src/lib_base/fitness.ml b/src/lib_base/fitness.ml
index f47174620..935241df2 100644
--- a/src/lib_base/fitness.ml
+++ b/src/lib_base/fitness.ml
@@ -52,7 +52,8 @@ let rec pp fmt = function
 
 let encoding =
   let open Data_encoding in
-  describe ~title: "Tezos block fitness"
+  def "fitness"
+    ~title: "Tezos block fitness"
     (list bytes)
 
 let to_bytes v = Data_encoding.Binary.to_bytes_exn encoding v
diff --git a/src/lib_base/test_chain_status.ml b/src/lib_base/test_chain_status.ml
index 0f6bc221e..5d39a5777 100644
--- a/src/lib_base/test_chain_status.ml
+++ b/src/lib_base/test_chain_status.ml
@@ -22,7 +22,7 @@ type t =
 
 let encoding =
   let open Data_encoding in
-  describe ~title:"Test chain status" @@
+  def "test_chain_status" @@
   union [
     case (Tag 0) ~name:"Not_running"
       (obj1 (req "status" (constant "not_running")))
diff --git a/src/lib_base/time.ml b/src/lib_base/time.ml
index b3f2d5fc6..68a55864e 100644
--- a/src/lib_base/time.ml
+++ b/src/lib_base/time.ml
@@ -78,8 +78,7 @@ module T = struct
   let rfc_encoding =
     let open Data_encoding in
     def
-      "timestamp" @@
-    describe
+      "timestamp.rfc"
       ~title:
         "RFC 3339 formatted timestamp"
       ~description:
@@ -93,7 +92,7 @@ module T = struct
 
   let encoding =
     let open Data_encoding in
-    describe ~title:"timestamp" @@
+    def "timestamp" @@
     splitted
       ~binary: int64
       ~json:
diff --git a/src/lib_crypto/helpers.ml b/src/lib_crypto/helpers.ml
index 14afbe1f1..131c9ff2b 100644
--- a/src/lib_crypto/helpers.ml
+++ b/src/lib_crypto/helpers.ml
@@ -103,7 +103,8 @@ module MakeEncoder(H : sig
       ~binary:
         H.raw_encoding
       ~json:
-        (describe ~title: (H.title ^ " (Base58Check-encoded)") @@
+        (def H.title
+           ~title: (H.title ^ " (Base58Check-encoded)") @@
          conv
            H.to_b58check
            (Data_encoding.Json.wrap_error H.of_b58check_exn)
diff --git a/src/lib_crypto/signature.ml b/src/lib_crypto/signature.ml
index ce9467d4c..fb53e0e90 100644
--- a/src/lib_crypto/signature.ml
+++ b/src/lib_crypto/signature.ml
@@ -47,6 +47,7 @@ module Public_key_hash = struct
 
   let raw_encoding =
     let open Data_encoding in
+    def "public_key_hash" ~description:title @@
     union [
       case (Tag 0) Ed25519.Public_key_hash.encoding
         (function Ed25519 x -> Some x | _ -> None)
@@ -230,6 +231,7 @@ module Public_key = struct
       let title = title
       let raw_encoding =
         let open Data_encoding in
+        def "public_key" ~description:title @@
         union [
           case (Tag 0) Ed25519.Public_key.encoding
             (function Ed25519 x -> Some x | _ -> None)
@@ -312,6 +314,7 @@ module Secret_key = struct
       let title = title
       let raw_encoding =
         let open Data_encoding in
+        def "secret_key" ~description:title @@
         union [
           case (Tag 0) Ed25519.Secret_key.encoding
             (function Ed25519 x -> Some x | _ -> None)
diff --git a/src/lib_data_encoding/binary_length.ml b/src/lib_data_encoding/binary_length.ml
index 6e564793e..338b11331 100644
--- a/src/lib_data_encoding/binary_length.ml
+++ b/src/lib_data_encoding/binary_length.ml
@@ -62,7 +62,7 @@ let rec length : type x. x Encoding.t -> x -> int =
                   let tag_size = Binary_size.tag_size sz in
                   tag_size + length e value in
         length_case cases
-    | Mu (`Dynamic, _name, self) ->
+    | Mu (`Dynamic, _name, _, _, self) ->
         length (self e) value
     | Obj (Opt { kind = `Dynamic ; encoding = e }) -> begin
         match value with
@@ -103,7 +103,7 @@ let rec length : type x. x Encoding.t -> x -> int =
                   let tag_size = Binary_size.tag_size sz in
                   tag_size + length e value in
         length_case cases
-    | Mu (`Variable, _name, self) ->
+    | Mu (`Variable, _name, _, _, self) ->
         length (self e) value
     (* Recursive*)
     | Obj (Req { encoding = e }) -> length e value
@@ -112,7 +112,6 @@ let rec length : type x. x Encoding.t -> x -> int =
     | Conv  { encoding = e ; proj } ->
         length e (proj value)
     | Describe { encoding = e } -> length e value
-    | Def { encoding = e } -> length e value
     | Splitted { encoding = e } -> length e value
     | Dynamic_size { kind ; encoding = e } ->
         let length = length e value in
diff --git a/src/lib_data_encoding/binary_reader.ml b/src/lib_data_encoding/binary_reader.ml
index 36625f406..a496483a1 100644
--- a/src/lib_data_encoding/binary_reader.ml
+++ b/src/lib_data_encoding/binary_reader.ml
@@ -271,9 +271,8 @@ let rec read_rec : type ret. ret Encoding.t -> state -> ret
         state.allowed_bytes <- allowed_bytes ;
         v
     | Describe { encoding = e } -> read_rec e state
-    | Def { encoding = e } -> read_rec e state
     | Splitted { encoding = e } -> read_rec e state
-    | Mu (_, _, self) -> read_rec (self e) state
+    | Mu (_, _, _, _, self) -> read_rec (self e) state
     | Delayed f -> read_rec (f ()) state
 
 
diff --git a/src/lib_data_encoding/binary_stream_reader.ml b/src/lib_data_encoding/binary_stream_reader.ml
index 3dacdfe35..a522b4615 100644
--- a/src/lib_data_encoding/binary_stream_reader.ml
+++ b/src/lib_data_encoding/binary_stream_reader.ml
@@ -340,9 +340,8 @@ let rec read_rec
               Some (old_limit - read) in
         k (v, { state with allowed_bytes })
     | Describe { encoding = e } -> read_rec e state k
-    | Def { encoding = e } -> read_rec e state k
     | Splitted { encoding = e } -> read_rec e state k
-    | Mu (_, _, self) -> read_rec (self e) state k
+    | Mu (_, _, _, _, self) -> read_rec (self e) state k
     | Delayed f -> read_rec (f ()) state k
 
 and remaining_bytes { remaining_bytes } =
diff --git a/src/lib_data_encoding/binary_writer.ml b/src/lib_data_encoding/binary_writer.ml
index 189dc546a..f9f3b07a9 100644
--- a/src/lib_data_encoding/binary_writer.ml
+++ b/src/lib_data_encoding/binary_writer.ml
@@ -272,9 +272,8 @@ let rec write_rec : type a. a Encoding.t -> state -> a -> unit =
     | Check_size { limit ; encoding = e } ->
         write_with_limit limit e state value
     | Describe { encoding = e } -> write_rec e state value
-    | Def { encoding = e } -> write_rec e state value
     | Splitted { encoding = e } -> write_rec e state value
-    | Mu (_, _, self) -> write_rec (self e) state value
+    | Mu (_, _, _, _, self) -> write_rec (self e) state value
     | Delayed f -> write_rec (f ()) state value
 
 and write_with_limit : type a. int -> a Encoding.t -> state -> a -> unit =
diff --git a/src/lib_data_encoding/data_encoding.mli b/src/lib_data_encoding/data_encoding.mli
index 6c9ea00c1..bdb997942 100644
--- a/src/lib_data_encoding/data_encoding.mli
+++ b/src/lib_data_encoding/data_encoding.mli
@@ -447,18 +447,21 @@ module Encoding: sig
   val splitted : json:'a encoding -> binary:'a encoding -> 'a encoding
 
   (** Combinator for recursive encodings. *)
-  val mu : string -> ('a encoding -> 'a encoding) -> 'a encoding
+  val mu :
+    string ->
+    ?title: string ->
+    ?description: string ->
+    ('a encoding -> 'a encoding) -> 'a encoding
 
   (** {3 Documenting descriptors} *)
 
-  (** Add documentation to an encoding. *)
-  val describe :
+  (** Give a name to an encoding and optionnaly
+      add documentation to an encoding. *)
+  val def :
+    string ->
     ?title:string -> ?description:string ->
     't encoding ->'t encoding
 
-  (** Give a name to an encoding. *)
-  val def : string -> 'a encoding -> 'a encoding
-
   (** See {!lazy_encoding} below.*)
   type 'a lazy_t
 
diff --git a/src/lib_data_encoding/encoding.ml b/src/lib_data_encoding/encoding.ml
index 23146e1a1..8deb42ea3 100644
--- a/src/lib_data_encoding/encoding.ml
+++ b/src/lib_data_encoding/encoding.ml
@@ -91,18 +91,17 @@ type 'a desc =
   | Tup : 'a t -> 'a desc
   | Tups : Kind.t * 'a t * 'b t -> ('a * 'b) desc
   | Union : Kind.t * Binary_size.tag_size * 'a case list -> 'a desc
-  | Mu : Kind.enum * string * ('a t -> 'a t) -> 'a desc
+  | Mu : Kind.enum * string * string option * string option * ('a t -> 'a t) -> 'a desc
   | Conv :
       { proj : ('a -> 'b) ;
         inj : ('b -> 'a) ;
         encoding : 'b t ;
         schema : Json_schema.schema option } -> 'a desc
   | Describe :
-      { title : string option ;
+      { id : string ;
+        title : string option ;
         description : string option ;
         encoding : 'a t } -> 'a desc
-  | Def : { name : string ;
-            encoding : 'a t } -> 'a desc
   | Splitted :
       { encoding : 'a t ;
         json_encoding : 'a Json_encoding.encoding ;
@@ -116,15 +115,21 @@ type 'a desc =
 and _ field =
   | Req : { name: string ;
             encoding: 'a t ;
+            title: string option ;
+            description: string option ;
           } -> 'a field
   | Opt : { name: string ;
             kind: Kind.enum ;
             encoding: 'a t ;
+            title: string option ;
+            description: string option ;
           } -> 'a option field
   | Dft : { name: string ;
             encoding: 'a t ;
             default: 'a ;
-         } -> 'a field
+            title: string option ;
+            description: string option ;
+          } -> 'a field
 
 and 'a case =
   | Case : { name : string option ;
@@ -169,7 +174,7 @@ let rec classify : type a. a t -> Kind.t = fun e ->
   | Objs (kind, _, _) -> kind
   | Tups (kind, _, _) -> kind
   | Union (kind, _, _) -> (kind :> Kind.t)
-  | Mu (kind, _, _) -> (kind :> Kind.t)
+  | Mu (kind, _, _, _ , _) -> (kind :> Kind.t)
   (* Variable *)
   | Ignore -> `Fixed 0
   | Array _ -> `Variable
@@ -180,7 +185,6 @@ let rec classify : type a. a t -> Kind.t = fun e ->
   | Tup encoding -> classify encoding
   | Conv { encoding } -> classify encoding
   | Describe { encoding } -> classify encoding
-  | Def { encoding } -> classify encoding
   | Splitted { encoding } -> classify encoding
   | Dynamic_size _ -> `Dynamic
   | Check_size { encoding } -> classify encoding
@@ -241,11 +245,10 @@ let rec is_zeroable: type t. t encoding -> bool = fun e ->
   | Tups (_, e1, e2) -> is_zeroable e1 && is_zeroable e2
   | Union (_, _, _) -> false (* includes a tag *)
   (* other recursive cases: truth propagates *)
-  | Mu (`Dynamic, _, _) -> false (* size prefix *)
-  | Mu (`Variable, _, f) -> is_zeroable (f e)
+  | Mu (`Dynamic, _, _, _ ,_) -> false (* size prefix *)
+  | Mu (`Variable, _, _, _, f) -> is_zeroable (f e)
   | Conv { encoding } -> is_zeroable encoding
   | Describe { encoding } -> is_zeroable encoding
-  | Def { encoding } -> is_zeroable encoding
   | Splitted { encoding } -> is_zeroable encoding
   | Check_size { encoding } -> is_zeroable encoding
   (* Unscrutable: true by default *)
@@ -331,29 +334,21 @@ let string_enum = function
 let conv proj inj ?schema encoding =
   make @@ Conv { proj ; inj ; encoding ; schema }
 
-let describe ?title ?description encoding =
-  match title, description with
-  | None, None -> encoding
-  | _, _ -> make @@ Describe { title ; description ; encoding }
-
-let def name encoding = make @@ Def { name ; encoding }
+let def id ?title ?description encoding =
+  make @@ Describe { id ; title ; description ; encoding }
 
 let req ?title ?description n t =
-  Req { name = n ; encoding = describe ?title ?description t }
+  Req { name = n ; encoding = t ; title ; description }
 let opt ?title ?description n encoding =
   let kind =
     match classify encoding with
     | `Variable -> `Variable
     | `Fixed _ | `Dynamic -> `Dynamic in
-  Opt { name = n ; kind ;
-        encoding = make @@ Describe { title ; description ; encoding } }
+  Opt { name = n ; kind ; encoding ; title ; description }
 let varopt ?title ?description n encoding =
-  Opt { name = n ; kind = `Variable ;
-        encoding = make @@ Describe { title ; description ; encoding } }
+  Opt { name = n ; kind = `Variable ; encoding ; title ; description }
 let dft ?title ?description n t d =
-  Dft { name = n ;
-        encoding = describe ?title ?description t ;
-        default = d }
+  Dft { name = n ; encoding = t ; default = d ; title ; description }
 
 let raw_splitted ~json ~binary =
   make @@ Splitted { encoding = binary ;
@@ -371,11 +366,10 @@ let rec is_obj : type a. a t -> bool = fun e ->
       List.for_all (fun (Case { encoding = e }) -> is_obj e) cases
   | Empty -> true
   | Ignore -> true
-  | Mu (_,_,self) -> is_obj (self e)
+  | Mu (_,_,_,_,self) -> is_obj (self e)
   | Splitted { is_obj } -> is_obj
   | Delayed f -> is_obj (f ())
   | Describe { encoding } -> is_obj encoding
-  | Def { encoding } -> is_obj encoding
   | _ -> false
 
 let rec is_tup : type a. a t -> bool = fun e ->
@@ -386,11 +380,10 @@ let rec is_tup : type a. a t -> bool = fun e ->
   | Dynamic_size { encoding = e } -> is_tup e
   | Union (_,_,cases) ->
       List.for_all (function Case { encoding = e} -> is_tup e) cases
-  | Mu (_,_,self) -> is_tup (self e)
+  | Mu (_,_,_,_,self) -> is_tup (self e)
   | Splitted { is_tup } -> is_tup
   | Delayed f -> is_tup (f ())
   | Describe { encoding } -> is_tup encoding
-  | Def { encoding } -> is_tup encoding
   | _ -> false
 
 let raw_merge_objs e1 e2 =
@@ -580,10 +573,9 @@ let rec is_nullable: type t. t encoding -> bool = fun e ->
   | Tups _ -> false
   | Union (_, _, cases) ->
       List.exists (fun (Case { encoding = e }) -> is_nullable e) cases
-  | Mu (_, _, f) -> is_nullable (f e)
+  | Mu (_, _, _, _, f) -> is_nullable (f e)
   | Conv { encoding = e } -> is_nullable e
   | Describe { encoding = e } -> is_nullable e
-  | Def { encoding = e } -> is_nullable e
   | Splitted { json_encoding } -> Json_encoding.is_nullable json_encoding
   | Dynamic_size { encoding = e } -> is_nullable e
   | Check_size { encoding = e } -> is_nullable e
@@ -604,16 +596,16 @@ let option ty =
         (function None -> Some () | Some _ -> None)
         (fun () -> None) ;
     ]
-let mu name self =
+let mu name ?title ?description self =
   let kind =
     try
-      match classify (self (make @@ Mu (`Dynamic, name, self))) with
+      match classify (self (make @@ Mu (`Dynamic, name, title, description, self))) with
       | `Fixed _ | `Dynamic -> `Dynamic
       | `Variable -> raise Exit
     with Exit | _ (* TODO variability error *) ->
-      ignore @@ classify (self (make @@ Mu (`Variable, name, self))) ;
+      ignore @@ classify (self (make @@ Mu (`Variable, name, title, description, self))) ;
       `Variable in
-  make @@ Mu (kind, name, self)
+  make @@ Mu (kind, name, title, description, self)
 
 let result ok_enc error_enc =
   union
diff --git a/src/lib_data_encoding/encoding.mli b/src/lib_data_encoding/encoding.mli
index 7c21ccf66..6e6167fce 100644
--- a/src/lib_data_encoding/encoding.mli
+++ b/src/lib_data_encoding/encoding.mli
@@ -49,18 +49,17 @@ type 'a desc =
   | Tup : 'a t -> 'a desc
   | Tups : Kind.t * 'a t * 'b t -> ('a * 'b) desc
   | Union : Kind.t * Binary_size.tag_size * 'a case list -> 'a desc
-  | Mu : Kind.enum * string * ('a t -> 'a t) -> 'a desc
+  | Mu : Kind.enum * string * string option * string option * ('a t -> 'a t) -> 'a desc
   | Conv :
       { proj : ('a -> 'b) ;
         inj : ('b -> 'a) ;
         encoding : 'b t ;
         schema : Json_schema.schema option } -> 'a desc
   | Describe :
-      { title : string option ;
+      { id : string ;
+        title : string option ;
         description : string option ;
         encoding : 'a t } -> 'a desc
-  | Def : { name : string ;
-            encoding : 'a t } -> 'a desc
   | Splitted :
       { encoding : 'a t ;
         json_encoding : 'a Json_encoding.encoding ;
@@ -74,15 +73,21 @@ type 'a desc =
 and _ field =
   | Req : { name: string ;
             encoding: 'a t ;
+            title: string option ;
+            description: string option ;
           } -> 'a field
   | Opt : { name: string ;
             kind: Kind.enum ;
             encoding: 'a t ;
+            title: string option ;
+            description: string option ;
           } -> 'a option field
   | Dft : { name: string ;
             encoding: 'a t ;
             default: 'a ;
-         } -> 'a field
+            title: string option ;
+            description: string option ;
+          } -> 'a field
 
 and 'a case =
   | Case : { name : string option ;
@@ -234,16 +239,20 @@ val case :
 val union :
   ?tag_size:[ `Uint8 | `Uint16 ] -> 't case list -> 't encoding
 
-val describe :
+val def :
+  string ->
   ?title:string -> ?description:string ->
-  't encoding ->'t encoding
-val def : string -> 'a encoding -> 'a encoding
+  'a encoding -> 'a encoding
 
 val conv :
   ('a -> 'b) -> ('b -> 'a) ->
   ?schema:Json_schema.schema ->
   'b encoding -> 'a encoding
-val mu : string -> ('a encoding -> 'a encoding) -> 'a encoding
+val mu :
+  string ->
+  ?title:string ->
+  ?description: string ->
+  ('a encoding -> 'a encoding) -> 'a encoding
 
 val classify : 'a encoding -> [ `Fixed of int | `Dynamic | `Variable ]
 val raw_splitted : json:'a Json_encoding.encoding -> binary:'a encoding -> 'a encoding
diff --git a/src/lib_data_encoding/json.ml b/src/lib_data_encoding/json.ml
index 2b03fe5f0..c238312f0 100644
--- a/src/lib_data_encoding/json.ml
+++ b/src/lib_data_encoding/json.ml
@@ -46,8 +46,7 @@ let int64_encoding =
 
 let n_encoding =
   let open Json_encoding in
-  def "positive_bignum" @@
-  describe
+  def "positive_bignum"
     ~title: "Positive big number"
     ~description: "Decimal representation of a positive big number" @@
   conv
@@ -64,8 +63,7 @@ let n_encoding =
 
 let z_encoding =
   let open Json_encoding in
-  def "bignum" @@
-  describe
+  def "bignum"
     ~title: "Big number"
     ~description: "Decimal representation of a big number" @@
   conv Z.to_string Z.of_string string
@@ -210,10 +208,9 @@ let rec json : type a. a Encoding.desc -> a Json_encoding.encoding =
   | Tups (_, e1, e2) ->
       merge_tups (get_json e1) (get_json e2)
   | Conv { proj ; inj ; encoding = e ; schema } -> conv ?schema proj inj (get_json e)
-  | Describe { title ; description ; encoding = e } ->
-      describe ?title ?description (get_json e)
-  | Def { name ; encoding = e } -> def name (get_json e)
-  | Mu (_, name, self) as ty ->
+  | Describe { id ; title ; description ; encoding = e } ->
+      def id ?title ?description (get_json e)
+  | Mu (_, name, _, _, self) as ty ->
       mu name (fun json_encoding -> get_json @@ self (make ~json_encoding ty))
   | Union (_tag_size, _, cases) -> union (List.map case_json cases)
   | Splitted { json_encoding } -> json_encoding
diff --git a/src/lib_error_monad/error_monad.ml b/src/lib_error_monad/error_monad.ml
index ee254090c..eda26a3fb 100644
--- a/src/lib_error_monad/error_monad.ml
+++ b/src/lib_error_monad/error_monad.ml
@@ -118,7 +118,7 @@ module Make(Prefix : sig val id : string end) = struct
     let encoding_case =
       let open Data_encoding in
       case Json_only
-        (describe ~title ~description @@
+        (def "generic_error" ~title ~description @@
          conv (fun x -> ((), x)) (fun ((), x) -> x) @@
          (obj2
             (req "kind" (constant "generic"))
@@ -186,7 +186,7 @@ module Make(Prefix : sig val id : string end) = struct
                  (req "id" (constant name)))
               encoding in
           case Json_only
-            (describe ~title ~description
+            (def name ~title ~description
                (conv (fun x -> (((), ()), x)) (fun (((),()), x) -> x)
                   with_id_and_kind_encoding))
             from_error to_error in
@@ -293,17 +293,17 @@ module Make(Prefix : sig val id : string end) = struct
   let result_encoding t_encoding =
     let open Data_encoding in
     let errors_encoding =
-      describe ~title: "An erroneous result" @@
       obj1 (req "error" (list error_encoding)) in
     let t_encoding =
-      describe ~title: "A successful result" @@
       obj1 (req "result" t_encoding) in
     union
       ~tag_size:`Uint8
       [ case (Tag 0) t_encoding
+          ~name:"A successful result"
           (function Ok x -> Some x | _ -> None)
           (function res -> Ok res) ;
         case (Tag 1) errors_encoding
+          ~name:"A erroneous result"
           (function Error x -> Some x | _ -> None)
           (fun errs -> Error errs) ]
 
@@ -552,7 +552,7 @@ module Make(Prefix : sig val id : string end) = struct
     let encoding_case =
       let open Data_encoding in
       case Json_only
-        (describe ~title ~description @@
+        (def "assertion" ~title ~description @@
          conv (fun (x, y) -> ((), x, y)) (fun ((), x, y) -> (x, y)) @@
          (obj3
             (req "kind" (constant "assertion"))
diff --git a/src/lib_micheline/micheline.ml b/src/lib_micheline/micheline.ml
index 6d36c1562..3f1b681fd 100644
--- a/src/lib_micheline/micheline.ml
+++ b/src/lib_micheline/micheline.ml
@@ -20,8 +20,7 @@ type 'p canonical = Canonical of (canonical_location, 'p) node
 let canonical_location_encoding =
   let open Data_encoding in
   def
-    "micheline.location" @@
-  describe
+    "micheline.location"
     ~title:
       "Canonical location in a Micheline expression"
     ~description:
@@ -141,8 +140,6 @@ let canonical_encoding ~variant prim_encoding =
               | _ -> None)
       (fun (prim, args, annot) -> Prim (0, prim, args, annot)) in
   let node_encoding = mu ("micheline." ^ variant ^ ".expression") (fun expr_encoding ->
-      describe
-        ~title: ("Micheline expression (" ^ variant ^ " variant)") @@
       splitted
         ~json:(union ~tag_size:`Uint8
                  [ int_encoding Json_only;
diff --git a/src/lib_protocol_environment/sigs/v1/data_encoding.mli b/src/lib_protocol_environment/sigs/v1/data_encoding.mli
index cb05f2b90..48be656a3 100644
--- a/src/lib_protocol_environment/sigs/v1/data_encoding.mli
+++ b/src/lib_protocol_environment/sigs/v1/data_encoding.mli
@@ -171,18 +171,22 @@ val case :
 val union :
   ?tag_size:[ `Uint8 | `Uint16 ] -> 't case list -> 't encoding
 
-val describe :
-  ?title:string -> ?description:string ->
+val def :
+  string ->
+  ?title:string ->
+  ?description:string ->
   't encoding ->'t encoding
 
-val def : string -> 'a encoding -> 'a encoding
-
 val conv :
   ('a -> 'b) -> ('b -> 'a) ->
   ?schema:json_schema ->
   'b encoding -> 'a encoding
 
-val mu : string -> ('a encoding -> 'a encoding) -> 'a encoding
+val mu :
+  string ->
+  ?title:string ->
+  ?description:string ->
+  ('a encoding -> 'a encoding) -> 'a encoding
 
 type 'a lazy_t
 
diff --git a/src/lib_rpc/RPC_service.ml b/src/lib_rpc/RPC_service.ml
index c6ced6336..ee4cbe215 100644
--- a/src/lib_rpc/RPC_service.ml
+++ b/src/lib_rpc/RPC_service.ml
@@ -54,17 +54,18 @@ let error_encoding =
       match !error_path with
       | None -> assert false
       | Some p -> p in
-    describe
+    def
+      "error"
       ~description:
         (Printf.sprintf
            "The full list of error is available with \
             the global RPC `%s %s`"
-           (string_of_meth meth) (Uri.path_and_query uri))
-      (conv
-         ~schema:Json_schema.any
-         (fun exn -> `A (List.map Error_monad.json_of_error exn))
-         (function `A exns -> List.map Error_monad.error_of_json exns | _ -> [])
-         json)
+           (string_of_meth meth) (Uri.path_and_query uri)) @@
+    conv
+      ~schema:Json_schema.any
+      (fun exn -> `A (List.map Error_monad.json_of_error exn))
+      (function `A exns -> List.map Error_monad.error_of_json exns | _ -> [])
+      json
   end
 
 let get_service = get_service ~error:error_encoding
diff --git a/src/lib_shell_services/block_services.ml b/src/lib_shell_services/block_services.ml
index e0652b638..3817870ab 100644
--- a/src/lib_shell_services/block_services.ml
+++ b/src/lib_shell_services/block_services.ml
@@ -95,11 +95,9 @@ let pp_block_info ppf
 
 let block_info_encoding =
   let operation_encoding =
-    describe ~title:"Operation hash" @@
     merge_objs
       (obj1 (req "hash" Operation_hash.encoding))
       Operation.encoding in
-  describe ~title:"Block info" @@
   conv
     (fun { hash ; chain_id ; level ; proto_level ; predecessor ;
            fitness ; timestamp ; protocol ;
@@ -138,7 +136,6 @@ type preapply_result = {
 }
 
 let preapply_result_encoding =
-  describe ~title:"Preapply result" @@
   (conv
      (fun { shell_header ; operations } ->
         (shell_header, operations))
@@ -191,7 +188,7 @@ module S = struct
     RPC_service.post_service
       ~description:"All the information about a block."
       ~query: RPC_query.empty
-      ~input: (describe ~title:"Operations" (obj1 (dft "operations" bool true)))
+      ~input: (obj1 (dft "operations" bool true))
       ~output: block_info_encoding
       block_path
 
@@ -200,7 +197,7 @@ module S = struct
       ~description:"Returns the chain in which the block belongs."
       ~query: RPC_query.empty
       ~input: empty
-      ~output: (describe ~title:"Chain ID" (obj1 (req "chain_id" Chain_id.encoding)))
+      ~output: (obj1 (req "chain_id" Chain_id.encoding))
       RPC_path.(block_path / "chain_id")
 
   let level =
@@ -208,7 +205,7 @@ module S = struct
       ~description:"Returns the block's level."
       ~query: RPC_query.empty
       ~input: empty
-      ~output: (describe ~title:"Level" (obj1 (req "level" int32)))
+      ~output: (obj1 (req "level" int32))
       RPC_path.(block_path / "level")
 
   let predecessor =
@@ -216,7 +213,7 @@ module S = struct
       ~description:"Returns the previous block's id."
       ~query: RPC_query.empty
       ~input: empty
-      ~output: (describe ~title:"Predecessor" (obj1 (req "predecessor" Block_hash.encoding)))
+      ~output: (obj1 (req "predecessor" Block_hash.encoding))
       RPC_path.(block_path / "predecessor")
 
   let predecessors =
@@ -224,10 +221,8 @@ module S = struct
       ~description:
         "...."
       ~query: RPC_query.empty
-      ~input: (describe ~title:"Num predecessors" (obj1 (req "length" Data_encoding.uint16)))
-      ~output:(describe ~title:"Block hash list"
-                 (obj1
-                    (req "blocks" (list Block_hash.encoding))))
+      ~input: (obj1 (req "length" Data_encoding.uint16))
+      ~output: (obj1 (req "blocks" (list Block_hash.encoding)))
       RPC_path.(block_path / "predecessors")
 
   let hash =
@@ -243,7 +238,7 @@ module S = struct
       ~description:"Returns the block's fitness."
       ~query: RPC_query.empty
       ~input: empty
-      ~output: (describe ~title:"Fitness" (obj1 (req "fitness" Fitness.encoding)))
+      ~output: (obj1 (req "fitness" Fitness.encoding))
       RPC_path.(block_path / "fitness")
 
   let context =
@@ -251,7 +246,7 @@ module S = struct
       ~description:"Returns the hash of the resulting context."
       ~query: RPC_query.empty
       ~input: empty
-      ~output: (describe ~title:"Context hash" (obj1 (req "context" Context_hash.encoding)))
+      ~output: (obj1 (req "context" Context_hash.encoding))
       RPC_path.(block_path / "context")
 
   let raw_context_args : string RPC_arg.t =
@@ -263,7 +258,6 @@ module S = struct
 
   let raw_context_result_encoding : raw_context_result Data_encoding.t =
     let open Data_encoding in
-    describe ~title:"Raw Context" @@
     obj1 (req "content"
             (mu "context_tree" (fun raw_context_result_encoding ->
                  union [
@@ -301,7 +295,7 @@ module S = struct
       ~description:"Returns the block's timestamp."
       ~query: RPC_query.empty
       ~input: empty
-      ~output:(describe ~title:"Timestamp" (obj1 (req "timestamp" Time.encoding)))
+      ~output: (obj1 (req "timestamp" Time.encoding))
       RPC_path.(block_path / "timestamp")
 
   type operations_param = {
@@ -310,7 +304,7 @@ module S = struct
 
   let operations_param_encoding =
     let open Data_encoding in
-    describe ~title:"Operations param" @@
+    def "next_operation" @@
     conv
       (fun { contents } -> (contents))
       (fun (contents) -> { contents })
@@ -322,17 +316,14 @@ module S = struct
       ~query: RPC_query.empty
       ~input: operations_param_encoding
       ~output:
-        (describe ~title:"Operations" @@
-         obj1
+        (obj1
            (req "operations"
               (list
-                 (describe ~title:"Operation/operation hash pair list"
-                    (list
-                       (describe ~title:"Operation, operation hash pairs"
-                          (obj2
-                             (req "hash" Operation_hash.encoding)
-                             (opt "contents"
-                                (dynamic_size Operation.encoding)))))))))
+                 (list
+                    (obj2
+                       (req "hash" Operation_hash.encoding)
+                       (opt "contents"
+                          (dynamic_size Operation.encoding)))))))
       RPC_path.(block_path / "operations")
 
   let protocol =
@@ -340,8 +331,7 @@ module S = struct
       ~description:"List the block protocol."
       ~query: RPC_query.empty
       ~input: empty
-      ~output: (describe ~title:"Block protocol"
-                  (obj1 (req "protocol" Protocol_hash.encoding)))
+      ~output: (obj1 (req "protocol" Protocol_hash.encoding))
       RPC_path.(block_path / "protocol")
 
   let test_chain =
@@ -360,7 +350,6 @@ module S = struct
   }
 
   let preapply_param_encoding =
-    describe ~title:"Preapply param" @@
     (conv
        (fun { timestamp ; protocol_data ; operations ; sort_operations } ->
           (timestamp, protocol_data, operations, sort_operations))
@@ -393,7 +382,7 @@ module S = struct
                      block, operations, public_keys and contracts."
       ~query: RPC_query.empty
       ~input: empty
-      ~output: (describe ~title:"String list" (list string))
+      ~output: (list string)
       RPC_path.(block_path / "complete" /: prefix_arg )
 
   type list_param = {
@@ -406,7 +395,6 @@ module S = struct
     min_heads: int option;
   }
   let list_param_encoding =
-    describe ~title:"List blocks param" @@
     conv
       (fun { include_ops ; length ; heads ; monitor ;
              delay ; min_date ; min_heads } ->
@@ -417,50 +405,43 @@ module S = struct
           delay ; min_date ; min_heads })
       (obj7
          (dft "include_ops"
-            (Data_encoding.describe
-               ~description:
-                 "Whether the resulting block informations should include the \
-                  list of operations' hashes. Default false."
-               bool) false)
+            ~description:
+              "Whether the resulting block informations should include the \
+               list of operations' hashes. Default false."
+            bool false)
          (opt "length"
-            (Data_encoding.describe
-               ~description:
-                 "The requested number of predecessors to returns (per \
-                  requested head)."
-               int31))
+            ~description:
+              "The requested number of predecessors to returns (per \
+               requested head)."
+            int31)
          (opt "heads"
-            (Data_encoding.describe
-               ~description:
-                 "An empty argument requests blocks from the current heads. \
-                  A non empty list allow to request specific fragment \
-                  of the chain."
-               (list Block_hash.encoding)))
+            ~description:
+              "An empty argument requests blocks from the current heads. \
+               A non empty list allow to request specific fragment \
+               of the chain."
+            (list Block_hash.encoding))
          (opt "monitor"
-            (Data_encoding.describe
-               ~description:
-                 "When true, the socket is \"kept alive\" after the first \
-                  answer and new heads are streamed when discovered."
-               bool))
+            ~description:
+              "When true, the socket is \"kept alive\" after the first \
+               answer and new heads are streamed when discovered."
+            bool)
          (opt "delay"
-            (Data_encoding.describe
-               ~description:
-                 "By default only the blocks that were validated by the node \
-                  are considered. \
-                  When this optional argument is 0, only blocks with a \
-                  timestamp in the past are considered. Other values allows to \
-                  adjust the current time."
-               int31))
+            ~description:
+              "By default only the blocks that were validated by the node \
+               are considered. \
+               When this optional argument is 0, only blocks with a \
+               timestamp in the past are considered. Other values allows to \
+               adjust the current time."
+            int31)
          (opt "min_date"
-            (Data_encoding.describe
-               ~description: "When `min_date` is provided, heads with a \
-                              timestamp before `min_date` are filtered ouf"
-               Time.encoding))
+            ~description: "When `min_date` is provided, heads with a \
+                           timestamp before `min_date` are filtered ouf"
+            Time.encoding)
          (opt "min_heads"
-            (Data_encoding.describe
-               ~description:"When `min_date` is provided, returns at least \
-                             `min_heads` even when their timestamp is before \
-                             `min_date`."
-               int31)))
+            ~description:"When `min_date` is provided, returns at least \
+                          `min_heads` even when their timestamp is before \
+                          `min_date`."
+            int31))
 
   let list =
     RPC_service.post_service
@@ -481,11 +462,10 @@ module S = struct
       ~query: RPC_query.empty
       ~input:empty
       ~output:(Data_encoding.list
-                 (describe ~title:"Invalid block"
-                    (obj3
-                       (req "block" Block_hash.encoding)
-                       (req "level" int32)
-                       (req "errors" RPC_error.encoding))))
+                 (obj3
+                    (req "block" Block_hash.encoding)
+                    (req "level" int32)
+                    (req "errors" RPC_error.encoding)))
       RPC_path.(root / "invalid_blocks")
 
   let unmark_invalid =
diff --git a/src/lib_shell_services/block_validator_worker_state.ml b/src/lib_shell_services/block_validator_worker_state.ml
index 810df1acc..ec0435f7f 100644
--- a/src/lib_shell_services/block_validator_worker_state.ml
+++ b/src/lib_shell_services/block_validator_worker_state.ml
@@ -48,7 +48,6 @@ module Event = struct
 
   let encoding =
     let open Data_encoding in
-    describe ~title:"Event state" @@
     union
       [ case (Tag 0) ~name:"Debug"
           (obj1 (req "message" string))
diff --git a/src/lib_shell_services/protocol_services.ml b/src/lib_shell_services/protocol_services.ml
index 0cb60b0e9..0abd45c20 100644
--- a/src/lib_shell_services/protocol_services.ml
+++ b/src/lib_shell_services/protocol_services.ml
@@ -19,9 +19,7 @@ module S = struct
       ~query: RPC_query.empty
       ~input: empty
       ~output:
-        (obj1 (req "data"
-                 (describe ~title: "Tezos protocol"
-                    (Protocol.encoding))))
+        (obj1 (req "data" (Protocol.encoding)))
       RPC_path.(root / "protocols" /: protocols_arg)
 
   type list_param = {
diff --git a/src/lib_shell_services/shell_services.ml b/src/lib_shell_services/shell_services.ml
index 6153bb7b9..88244f150 100644
--- a/src/lib_shell_services/shell_services.ml
+++ b/src/lib_shell_services/shell_services.ml
@@ -36,24 +36,20 @@ module S = struct
       (obj5
          (req "data" bytes)
          (dft "blocking"
-            (describe
-               ~description:
-                 "Should the RPC wait for the block to be \
-                  validated before answering. (default: true)"
-               bool)
+            ~description:
+              "Should the RPC wait for the block to be \
+               validated before answering. (default: true)"
+            bool
             true)
          (dft "force"
-            (describe
-               ~description:
-                 "Should we inject the block when its fitness is below \
-                  the current head. (default: false)"
-               bool)
+            ~description:
+              "Should we inject the block when its fitness is below \
+               the current head. (default: false)"
+            bool
             false)
          (opt "chain_id" Chain_id.encoding)
          (req "operations"
-            (describe
-               ~description:"..."
-               (list (list (dynamic_size Operation.encoding))))))
+            (list (list (dynamic_size Operation.encoding)))))
 
   let inject_block =
     RPC_service.post_service
@@ -83,20 +79,17 @@ module S = struct
       ~input:
         (obj3
            (req "signedOperationContents"
-              (describe ~title: "Tezos signed operation (hex encoded)"
-                 bytes))
+              ~title: "Tezos signed operation (hex encoded)"
+              bytes)
            (dft "blocking"
-              (describe
-                 ~description:
-                   "Should the RPC wait for the operation to be \
-                    (pre-)validated before answering. (default: true)"
-                 bool)
+              ~description:
+                "Should the RPC wait for the operation to be \
+                 (pre-)validated before answering. (default: true)"
+              bool
               true)
            (opt "chain_id" Chain_id.encoding))
       ~output:
-        (describe
-           ~title: "Hash of the injected operation" @@
-         (obj1 (req "injectedOperation" Operation_hash.encoding)))
+        (obj1 (req "injectedOperation" Operation_hash.encoding))
       RPC_path.(root / "inject_operation")
 
   let inject_protocol =
@@ -106,24 +99,19 @@ module S = struct
       ~query: RPC_query.empty
       ~input:
         (obj3
-           (req "protocol"
-              (describe ~title: "Tezos protocol" Protocol.encoding))
+           (req "protocol" Protocol.encoding)
            (dft "blocking"
-              (describe
-                 ~description:
-                   "Should the RPC wait for the protocol to be \
-                    validated before answering. (default: true)"
-                 bool)
+              ~description:
+                "Should the RPC wait for the protocol to be \
+                 validated before answering. (default: true)"
+              bool
               true)
            (opt "force"
-              (describe
-                 ~description:
-                   "Should we inject protocol that is invalid. (default: false)"
-                 bool)))
+              ~description:
+                "Should we inject protocol that is invalid. (default: false)"
+              bool))
       ~output:
-        (describe
-           ~title: "Hash of the injected protocol" @@
-         (obj1 (req "injectedProtocol" Protocol_hash.encoding)))
+        (obj1 (req "injectedProtocol" Protocol_hash.encoding))
       RPC_path.(root / "inject_protocol")
 
   let bootstrapped =
diff --git a/src/proto_alpha/lib_protocol/src/contract_repr.ml b/src/proto_alpha/lib_protocol/src/contract_repr.ml
index b3065526e..0f56f6aee 100644
--- a/src/proto_alpha/lib_protocol/src/contract_repr.ml
+++ b/src/proto_alpha/lib_protocol/src/contract_repr.ml
@@ -48,7 +48,7 @@ let pp_short ppf = function
 
 let encoding =
   let open Data_encoding in
-  describe
+  def "contract_id"
     ~title:
       "A contract handle"
     ~description:
diff --git a/src/proto_alpha/lib_protocol/src/helpers_services.ml b/src/proto_alpha/lib_protocol/src/helpers_services.ml
index 840efa8da..4f174d68b 100644
--- a/src/proto_alpha/lib_protocol/src/helpers_services.ml
+++ b/src/proto_alpha/lib_protocol/src/helpers_services.ml
@@ -123,10 +123,9 @@ module S = struct
       ~description: "Levels of a cycle"
       ~query: RPC_query.empty
       ~input: empty
-      ~output: (describe ~title: "levels of a cycle"
-                  (obj2
-                     (req "first" Raw_level.encoding)
-                     (req "last" Raw_level.encoding)))
+      ~output:  (obj2
+                   (req "first" Raw_level.encoding)
+                   (req "last" Raw_level.encoding))
       RPC_path.(custom_root / "levels" /: Cycle.arg)
 
 end
@@ -263,8 +262,7 @@ module Forge = struct
         ~input: Operation.unsigned_operation_encoding
         ~output:
           (obj1
-             (req "operation" @@
-              describe ~title: "hex encoded operation" bytes))
+             (req "operation" bytes))
         RPC_path.(custom_root / "operations" )
 
     let empty_proof_of_work_nonce =
diff --git a/src/proto_alpha/lib_protocol/src/michelson_v1_primitives.ml b/src/proto_alpha/lib_protocol/src/michelson_v1_primitives.ml
index 428b7b545..33287f330 100644
--- a/src/proto_alpha/lib_protocol/src/michelson_v1_primitives.ml
+++ b/src/proto_alpha/lib_protocol/src/michelson_v1_primitives.ml
@@ -394,6 +394,7 @@ let strings_of_prims expr =
 
 let prim_encoding =
   let open Data_encoding in
+  def "michelson.v1.primitives" @@
   string_enum [
     ("parameter", K_parameter) ;
     ("storage", K_storage) ;
diff --git a/src/proto_alpha/lib_protocol/src/operation_repr.ml b/src/proto_alpha/lib_protocol/src/operation_repr.ml
index 5696c8234..b1fd86a45 100644
--- a/src/proto_alpha/lib_protocol/src/operation_repr.ml
+++ b/src/proto_alpha/lib_protocol/src/operation_repr.ml
@@ -113,7 +113,6 @@ module Encoding = struct
   open Data_encoding
 
   let reveal_encoding =
-    describe ~title:"Reveal operation" @@
     (obj2
        (req "kind" (constant "reveal"))
        (req "public_key" Signature.Public_key.encoding))
@@ -126,7 +125,6 @@ module Encoding = struct
       (fun ((), pkh) -> Reveal pkh)
 
   let transaction_encoding =
-    describe ~title:"Transaction operation" @@
     obj4
       (req "kind" (constant "transaction"))
       (req "amount" Tez_repr.encoding)
@@ -143,7 +141,6 @@ module Encoding = struct
          Transaction { amount ; destination ; parameters })
 
   let origination_encoding =
-    describe ~title:"Origination operation" @@
     (obj7
        (req "kind" (constant "origination"))
        (req "managerPubkey" Signature.Public_key_hash.encoding)
@@ -175,7 +172,6 @@ module Encoding = struct
             delegate ; script ; preorigination = None })
 
   let delegation_encoding =
-    describe ~title:"Delegation operation" @@
     (obj2
        (req "kind" (constant "delegation"))
        (opt "delegate" Signature.Public_key_hash.encoding))
@@ -419,11 +415,10 @@ module Encoding = struct
     mu_proto_operation_encoding operation_encoding
 
   let signed_proto_operation_encoding =
-    describe ~title:"Signed alpha operation" @@
     mu_signed_proto_operation_encoding operation_encoding
 
   let unsigned_operation_encoding =
-    describe ~title:"Unsigned Alpha operation" @@
+    def "operation.alpha.unsigned_operation" @@
     merge_objs
       Operation.shell_header_encoding
       proto_operation_encoding
diff --git a/src/proto_alpha/lib_protocol/src/qty_repr.ml b/src/proto_alpha/lib_protocol/src/qty_repr.ml
index 2b381c0de..ebc853e02 100644
--- a/src/proto_alpha/lib_protocol/src/qty_repr.ml
+++ b/src/proto_alpha/lib_protocol/src/qty_repr.ml
@@ -223,9 +223,7 @@ module Make (T: QTY) : S = struct
 
   let encoding =
     let open Data_encoding in
-    describe
-      ~title: "Amount in mutez"
-      (conv to_int64 (Json.wrap_error of_mutez_exn) int64)
+    (conv to_int64 (Json.wrap_error of_mutez_exn) int64)
 
   let () =
     let open Data_encoding in
diff --git a/src/proto_alpha/lib_protocol/src/script_repr.ml b/src/proto_alpha/lib_protocol/src/script_repr.ml
index 9ca409fdc..ed4c04308 100644
--- a/src/proto_alpha/lib_protocol/src/script_repr.ml
+++ b/src/proto_alpha/lib_protocol/src/script_repr.ml
@@ -57,6 +57,7 @@ type t = {
 
 let encoding =
   let open Data_encoding in
+  def "scripted.contracts" @@
   conv
     (fun { code ; storage } -> (code, storage))
     (fun (code, storage) -> { code ; storage })
diff --git a/src/proto_alpha/lib_protocol/src/script_tc_errors_registration.ml b/src/proto_alpha/lib_protocol/src/script_tc_errors_registration.ml
index 3a44290e7..24068706d 100644
--- a/src/proto_alpha/lib_protocol/src/script_tc_errors_registration.ml
+++ b/src/proto_alpha/lib_protocol/src/script_tc_errors_registration.ml
@@ -45,8 +45,7 @@ let () =
   let arity_enc =
     int8 in
   let namespace_enc =
-    def "primitiveNamespace" @@
-    describe
+    def "primitiveNamespace"
       ~title: "Primitive namespace"
       ~description:
         "One of the three possible namespaces of primitive \
@@ -55,8 +54,7 @@ let () =
                   "constant", Constant_namespace ;
                   "instruction", Instr_namespace ] in
   let kind_enc =
-    def "expressionKind" @@
-    describe
+    def "expressionKind"
       ~title: "Expression kind"
       ~description:
         "One of the four possible kinds of expression \
diff --git a/src/proto_alpha/lib_protocol/src/tez_repr.ml b/src/proto_alpha/lib_protocol/src/tez_repr.ml
index 97ff72c00..33564e6e9 100644
--- a/src/proto_alpha/lib_protocol/src/tez_repr.ml
+++ b/src/proto_alpha/lib_protocol/src/tez_repr.ml
@@ -12,3 +12,6 @@ include Qty_repr.Make (struct let id = "tez" end)
 type t = qty
 type tez = qty
 
+let encoding =
+  Data_encoding.def "mutez" @@
+  encoding
diff --git a/vendors/ocplib-json-typed/lib_json_typed/json_encoding.ml b/vendors/ocplib-json-typed/lib_json_typed/json_encoding.ml
index 2c75d58d3..42a2d1d62 100644
--- a/vendors/ocplib-json-typed/lib_json_typed/json_encoding.ml
+++ b/vendors/ocplib-json-typed/lib_json_typed/json_encoding.ml
@@ -69,10 +69,13 @@ type _ encoding =
   | Tups : 'a encoding * 'b encoding -> ('a * 'b) encoding
   | Custom : 't repr_agnostic_custom * Json_schema.schema -> 't encoding
   | Conv : ('a -> 'b) * ('b -> 'a) * 'b encoding * Json_schema.schema option -> 'a encoding
-  | Describe : { title: string option ;
+  | Describe : { id: string ;
+                 title: string option ;
                  description: string option ;
                  encoding: 'a encoding } -> 'a encoding
   | Mu : { id: string ;
+           title: string option ;
+           description: string option ;
            self: ('a encoding -> 'a encoding) ;
          }-> 'a encoding
   | Union : 't case list -> 't encoding
@@ -466,17 +469,12 @@ let schema encoding =
                           minimum = Some (minimum, `Inclusive) ;
                           maximum = Some (maximum, `Inclusive) })
       | Float None -> element (Number numeric_specs)
-      | Describe { title = None ; description = None ;
-                   encoding = t } -> schema t
-      | Describe { title = Some _ as title ; description =  None ;
-                   encoding = t } ->
-        { (schema t) with title }
-      | Describe  { title = None ; description =  Some _ as description ;
-                    encoding = t } ->
-        { (schema t) with description }
-      | Describe { title = Some _ as title ; description = Some _ as description ;
-                   encoding = t } ->
-        { (schema t) with title ; description }
+      | Describe { id = name ; title ; description ; encoding } ->
+          let open Json_schema in
+          let schema = patch_description ?title ?description (schema encoding) in
+          let s, def = add_definition name schema !sch in
+          sch := fst (merge_definitions (!sch, s)) ;
+          def
       | Custom (_, s) ->
         sch := fst (merge_definitions (!sch, s)) ;
         root s
@@ -484,7 +482,7 @@ let schema encoding =
         sch := fst (merge_definitions (!sch, s)) ;
         root s
       | Conv (_, _, t, None) -> schema t
-      | Mu { id = name ; self = f } ->
+      | Mu { id = name ; title ; description ; self = f } ->
         let fake_schema =
           if definition_exists name !sch then
             update (definition_ref name) !sch
@@ -495,7 +493,10 @@ let schema encoding =
           Custom ({ write = (fun _ _ -> assert false) ;
                     read = (fun _ -> assert false) },
                   fake_schema) in
-        let root = schema (f fake_self) in
+        let root =
+          patch_description
+            ?title ?description
+            (schema (f fake_self)) in
         let nsch, def = add_definition name root !sch in
         sch := nsch ; def
       | Array t ->
@@ -546,7 +547,7 @@ let opt ?title ?description n t =
 let dft ?title ?description n t d =
   Dft { name = n ; encoding = t ; title ; description ; default = d }
 
-let mu name self = Mu { id = name ; self }
+let mu name ?title ?description self = Mu { id = name ; title ; description ; self }
 let null = Null
 let int =
   Int { int_name = "int" ;
@@ -701,8 +702,6 @@ let tup10 f1 f2 f3 f4 f5 f6 f7 f8 f9 f10 =
 let repr_agnostic_custom { write ; read } ~schema =
   Custom ({ write ; read }, schema)
 
-let describe ?title ?description t = Describe { title ; encoding = t ; description }
-
 let constant s = Constant s
 
 let string_enum cases =
@@ -737,13 +736,8 @@ let string_enum cases =
     ~schema
     string
 
-let def name encoding =
-  let schema =
-    let open Json_schema in
-    let sch = schema encoding in
-    let sch, def = add_definition name (root sch) sch in
-    update def sch in
-  conv (fun v -> v) (fun v -> v) ~schema encoding
+let def id ?title ?description encoding =
+  Describe { id ; title ; description ; encoding }
 
 let assoc : type t. t encoding -> (string * t) list encoding = fun t ->
   Ezjsonm_encoding.custom
diff --git a/vendors/ocplib-json-typed/lib_json_typed/json_encoding.mli b/vendors/ocplib-json-typed/lib_json_typed/json_encoding.mli
index 3aae16d06..efcc777df 100644
--- a/vendors/ocplib-json-typed/lib_json_typed/json_encoding.mli
+++ b/vendors/ocplib-json-typed/lib_json_typed/json_encoding.mli
@@ -381,7 +381,11 @@ val conv :
              case (obj2 (req "hd" itemencoding) (req "tl" self))
                (function hd :: tl -> Some (hd, tl) | [] -> None)
                (fun (hd, tl) -> hd :: tl) ]) ]} *)
-val mu : string -> ('a encoding -> 'a encoding) -> 'a encoding
+val mu :
+  string ->
+  ?title: string ->
+  ?description: string ->
+  ('a encoding -> 'a encoding) -> 'a encoding
 
 (** A raw JSON value in ezjsonm representation. *)
 val any_ezjson_value : Json_repr.ezjsonm encoding
@@ -398,17 +402,14 @@ val any_schema : Json_schema.schema encoding
     May raise {!Bad_schema}. *)
 val schema : 't encoding -> Json_schema.schema
 
-(** Annotate a type with a title and description for the JSON schema. *)
-val describe :
-  ?title:string ->
-  ?description:string ->
-  't encoding ->
-  't encoding
-
 (** Name a definition so its occurences can be shared in the JSON
     schema.  The first parameter is a path, that must be unique and
     respect the format of {!Json_schema.add_definition}. *)
-val def : string -> 't encoding -> 't encoding
+val def :
+  string ->
+  ?title:string ->
+  ?description:string ->
+  't encoding -> 't encoding
 
 (** {2 Errors} *) (************************************************************)