diff --git a/src/client/client_aliases.ml b/src/client/client_aliases.ml
index cb5464cb6..19f2c45e7 100644
--- a/src/client/client_aliases.ml
+++ b/src/client/client_aliases.ml
@@ -33,16 +33,16 @@ module type Alias = sig
   val save : (Lwt_io.file_name * t) list -> unit Lwt.t
   val to_source : t -> string Lwt.t
   val alias_param :
-    ?n:string ->
+    ?name:string ->
     ?desc:string ->
     'a Cli_entries.params ->
     (Lwt_io.file_name * t -> 'a) Cli_entries.params
   val fresh_alias_param :
-    ?n:string ->
+    ?name:string ->
     ?desc:string ->
     'a Cli_entries.params -> (string -> 'a) Cli_entries.params
   val source_param :
-    ?n:string ->
+    ?name:string ->
     ?desc:string ->
     'a Cli_entries.params -> (t -> 'a) Cli_entries.params
 end
@@ -115,9 +115,8 @@ module Alias = functor (Entity : Entity) -> struct
     (if not Client_config.force#get then
        Lwt_list.iter_s (fun (n, v) ->
            if n = name && v = value then
-             (message "The %s alias %s already exists with the same value." Entity.name n ;
-              keep := true ;
-              return ())
+             (keep := true ;
+              message "The %s alias %s already exists with the same value." Entity.name n)
            else if n = name && v <> value then
              error "another %s is already aliased as %s, use -force true to update" Entity.name n
            else if n <> name && v = value then
@@ -130,8 +129,7 @@ module Alias = functor (Entity : Entity) -> struct
       return ()
     else
       save list >>= fun () ->
-      message "New %s alias '%s' saved." Entity.name name ;
-      return ()
+      message "New %s alias '%s' saved." Entity.name name
 
   let del name =
     load () >>= fun list ->
@@ -140,55 +138,56 @@ module Alias = functor (Entity : Entity) -> struct
 
   let save list =
     save list >>= fun () ->
-    message "Successful update of the %s alias file." Entity.name ;
-    return ()
+    message "Successful update of the %s alias file." Entity.name
 
   include Entity
 
-  let alias_param ?(n = "name") ?(desc = "existing " ^ name ^ " alias") next =
-    Param (n, desc, (fun s -> find s >>= fun v -> return (s, v)), next)
+  let alias_param ?(name = "name") ?(desc = "existing " ^ name ^ " alias") next =
+    param ~name ~desc
+      (fun s -> find s >>= fun v -> return (s, v))
+      next
 
-  let fresh_alias_param ?(n = "new") ?(desc = "new " ^ name ^ " alias") next =
-    Param (n,
-           desc,
-           (fun s ->
-              load () >>= fun list ->
-              if not Client_config.force#get then
-                Lwt_list.iter_s (fun (n, _v) ->
-                    if n = name then
-                      error "the %s alias %s already exists, use -force true to update" Entity.name n
-                    else return ())
-                  list >>= fun () ->
-                return s
-              else return s),
-           next)
+  let fresh_alias_param ?(name = "new") ?(desc = "new " ^ name ^ " alias") next =
+    param ~name ~desc
+      (fun s ->
+         load () >>= fun list ->
+         if not Client_config.force#get then
+           Lwt_list.iter_s (fun (n, _v) ->
+               if n = name then
+                 error "the %s alias %s already exists, use -force true to update" Entity.name n
+               else return ())
+             list >>= fun () ->
+           return s
+         else return s)
+      next
 
-  let source_param ?(n = "src") ?(desc = "source " ^ name) next =
-    Param (n,
-           desc ^ "\n"
-           ^ "can be an alias, file or litteral (autodetected in this order)\n\
-              use 'file:path', 'text:litteral' or 'alias:name' to force",
-           (fun s ->
-              let read path =
-                catch
-                  (fun () -> Lwt_io.(with_file ~mode:Input path read))
-                  (fun exn -> param_error "cannot read file (%s)" (Printexc.to_string exn))
-                >>= of_source in
-              match Utils.split ~limit:1 ':' s with
-              | [ "alias" ; alias ]->
-                  find alias
-              | [ "text" ; text ] ->
-                  of_source text
-              | [ "file" ; path ] ->
-                  read path
-              | _ ->
+  let source_param ?(name = "src") ?(desc = "source " ^ name) next =
+    let desc =
+      desc ^ "\n"
+      ^ "can be an alias, file or litteral (autodetected in this order)\n\
+         use 'file:path', 'text:litteral' or 'alias:name' to force" in
+    param ~name ~desc
+      (fun s ->
+         let read path =
+           catch
+             (fun () -> Lwt_io.(with_file ~mode:Input path read))
+             (fun exn -> Lwt.fail_with @@ Format.asprintf "cannot read file (%s)" (Printexc.to_string exn))
+           >>= of_source in
+         match Utils.split ~limit:1 ':' s with
+         | [ "alias" ; alias ]->
+             find alias
+         | [ "text" ; text ] ->
+             of_source text
+         | [ "file" ; path ] ->
+             read path
+         | _ ->
+             catch
+               (fun () -> find s)
+               (fun _ ->
                   catch
-                    (fun () -> find s)
-                    (fun _ ->
-                       catch
-                         (fun () -> read s)
-                         (fun _ -> of_source s))),
-           next)
+                    (fun () -> read s)
+                    (fun _ -> of_source s)))
+      next
 
    let name d =
      rev_find d >>= function
diff --git a/src/client/client_aliases.mli b/src/client/client_aliases.mli
index 70296652c..a8f75e8af 100644
--- a/src/client/client_aliases.mli
+++ b/src/client/client_aliases.mli
@@ -29,16 +29,16 @@ module type Alias = sig
   val save : (Lwt_io.file_name * t) list -> unit Lwt.t
   val to_source : t -> string Lwt.t
   val alias_param :
-    ?n:string ->
+    ?name:string ->
     ?desc:string ->
     'a Cli_entries.params ->
     (Lwt_io.file_name * t -> 'a) Cli_entries.params
   val fresh_alias_param :
-    ?n:string ->
+    ?name:string ->
     ?desc:string ->
     'a Cli_entries.params -> (string -> 'a) Cli_entries.params
   val source_param :
-    ?n:string ->
+    ?name:string ->
     ?desc:string ->
     'a Cli_entries.params -> (t -> 'a) Cli_entries.params
 end
diff --git a/src/client/client_generic_rpcs.ml b/src/client/client_generic_rpcs.ml
index 402b5ea94..22509b65a 100644
--- a/src/client/client_generic_rpcs.ml
+++ b/src/client/client_generic_rpcs.ml
@@ -332,9 +332,9 @@ let commands = Cli_entries.([
       ~desc: "list all understood protocol versions"
       (fixed [ "list" ; "versions" ])
       (fun () ->
-         List.iter
+         Lwt_list.iter_s
            (fun (ver, _) -> message "%a" Protocol_hash.pp_short ver)
-           (Client_version.get_versions ()) ; return ()) ;
+           (Client_version.get_versions ())) ;
     command
       ~tags: [ "low-level" ; "local" ]
       ~group: "rpc"
diff --git a/src/client/client_node_rpcs.ml b/src/client/client_node_rpcs.ml
index 247195539..def106a08 100644
--- a/src/client/client_node_rpcs.ml
+++ b/src/client/client_node_rpcs.ml
@@ -13,31 +13,13 @@ open Lwt
 open Cli_entries
 open Logging.RPC
 
-let log_file =
-  let open CalendarLib in
-  Printer.Precise_Calendar.sprint
-    "%Y-%m-%dT%H:%M:%SZ.log"
-    (Calendar.Precise.now ())
-
-let with_log_file f =
-  Utils.create_dir Client_config.(base_dir#get // "logs") >>= fun () ->
-  Lwt_io.with_file
-    ~flags: Unix.[ O_APPEND ; O_CREAT ; O_WRONLY ]
-    ~mode: Lwt_io.Output
-    Client_config.(base_dir#get // "logs" // log_file)
-    f
-
 let log_request cpt url req =
-  with_log_file
-    (fun fp ->
-       Lwt_io.fprintf fp">>>>%d: %s\n%s\n" cpt url req >>= fun () ->
-       Lwt_io.flush fp)
+  Cli_entries.log "requests"
+    ">>>>%d: %s\n%s\n" cpt url req
 
 let log_response cpt code ans =
-  with_log_file
-    (fun fp ->
-       Lwt_io.fprintf fp"<<<<%d: %s\n%s\n" cpt (Cohttp.Code.string_of_status code) ans >>= fun () ->
-       Lwt_io.flush fp)
+  Cli_entries.log "requests"
+    "<<<<%d: %s\n%s\n" cpt (Cohttp.Code.string_of_status code) ans
 
 let cpt = ref 0
 let make_request service json =
@@ -67,9 +49,10 @@ let get_streamed_json service json =
   let ansbody = Cohttp_lwt_body.to_stream ansbody in
   match code, ansbody with
   | #Cohttp.Code.success_status, ansbody ->
-      if Client_config.print_timings#get then
+      (if Client_config.print_timings#get then
         message "Request to /%s succeeded in %gs"
-          (String.concat "/" service) time ;
+          (String.concat "/" service) time
+       else Lwt.return ()) >>= fun () ->
       Lwt.return (
         Lwt_stream.filter_map_s
           (function
@@ -80,11 +63,12 @@ let get_streamed_json service json =
                 Lwt.return None)
           (Data_encoding.Json.from_stream ansbody))
   | err, _ansbody ->
-      if Client_config.print_timings#get then
+      (if Client_config.print_timings#get then
         message "Request to /%s failed in %gs"
-          (String.concat "/" service) time ;
+          (String.concat "/" service) time
+       else Lwt.return ()) >>= fun () ->
       message "Request to /%s failed, server returned %s"
-        (String.concat "/" service) (Cohttp.Code.string_of_status err) ;
+        (String.concat "/" service) (Cohttp.Code.string_of_status err) >>= fun () ->
       error "the RPC server returned a non-success status (%s)"
         (Cohttp.Code.string_of_status err)
 
@@ -93,9 +77,10 @@ let get_json service json =
   Cohttp_lwt_body.to_string ansbody >>= fun ansbody ->
   match code, ansbody with
   | #Cohttp.Code.success_status, ansbody -> begin
-      if Client_config.print_timings#get then
-        message "Request to /%s succeeded in %gs"
-          (String.concat "/" service) time ;
+      (if Client_config.print_timings#get then
+         message "Request to /%s succeeded in %gs"
+           (String.concat "/" service) time
+       else Lwt.return ()) >>= fun () ->
       log_response cpt code ansbody >>= fun () ->
       if ansbody = "" then Lwt.return `Null
       else match Data_encoding.Json.from_string ansbody with
@@ -103,11 +88,12 @@ let get_json service json =
         | Ok res -> Lwt.return res
     end
   | err, _ansbody ->
-      if Client_config.print_timings#get then
-        message "Request to /%s failed in %gs"
-          (String.concat "/" service) time ;
+      (if Client_config.print_timings#get then
+         message "Request to /%s failed in %gs"
+           (String.concat "/" service) time
+       else Lwt.return ()) >>= fun () ->
       message "Request to /%s failed, server returned %s"
-        (String.concat "/" service) (Cohttp.Code.string_of_status err) ;
+        (String.concat "/" service) (Cohttp.Code.string_of_status err) >>= fun () ->
       error "the RPC server returned a non-success status (%s)"
         (Cohttp.Code.string_of_status err)
 
diff --git a/src/client/client_protocols.ml b/src/client/client_protocols.ml
index b8a1213ff..d6d3e0afc 100644
--- a/src/client/client_protocols.ml
+++ b/src/client/client_protocols.ml
@@ -11,8 +11,8 @@ let commands () =
       ~desc: "list known protocols"
       (prefixes [ "list" ; "protocols" ] stop)
       (fun () ->
-         Client_node_rpcs.Protocols.list ~contents:false () >|= fun protos ->
-         List.iter (fun (ph, _p) -> message "%a" Protocol_hash.pp ph) protos
+         Client_node_rpcs.Protocols.list ~contents:false () >>= fun protos ->
+         Lwt_list.iter_s (fun (ph, _p) -> message "%a" Protocol_hash.pp ph) protos
       );
     command
       ~group: "protocols"
@@ -26,8 +26,7 @@ let commands () =
               let proto = Tezos_compiler.Protocol.of_dir dirname in
               Client_node_rpcs.inject_protocol proto >>= function
               | Ok hash ->
-                  message "Injected protocol %a successfully" Protocol_hash.pp_short hash;
-                  Lwt.return ();
+                  message "Injected protocol %a successfully" Protocol_hash.pp_short hash
               | Error err ->
                   error "Error while injecting protocol from %s: %a"
                     dirname Error_monad.pp_print_error err)
@@ -44,7 +43,7 @@ let commands () =
       (fun ph () ->
          Client_node_rpcs.Protocols.bytes ph >>= fun { data } -> match data with
          | Ok proto ->
-             Updater.extract "" ph proto >|= fun () ->
+             Updater.extract "" ph proto >>= fun () ->
              message "Extracted protocol %a" Protocol_hash.pp_short ph
          | Error err ->
              error "Error while dumping protocol %a: %a"
diff --git a/src/client/embedded/bootstrap/client_proto_args.ml b/src/client/embedded/bootstrap/client_proto_args.ml
index 2e3b66991..ac2f66c36 100644
--- a/src/client/embedded/bootstrap/client_proto_args.ml
+++ b/src/client/embedded/bootstrap/client_proto_args.ml
@@ -81,14 +81,14 @@ let delegatable_args =
     Arg.Clear delegatable,
     "Set the created contract to be non delegatable (default)" ]
 
-let tez_param ~n ~desc next =
+let tez_param ~name ~desc next =
   Cli_entries.param
-    n
+    name
     (desc ^ " in \xEA\x9C\xA9\n\
              text format: D,DDD,DDD.DD (centiles and comas are optional)")
     (fun s ->
        try Lwt.return (tez_of_string s)
-       with _ -> Cli_entries.param_error "invalid \xEA\x9C\xA9 notation")
+       with _ -> Lwt.fail_with "invalid \xEA\x9C\xA9 notation")
     next
 
 let max_priority = ref None
diff --git a/src/client/embedded/bootstrap/client_proto_args.mli b/src/client/embedded/bootstrap/client_proto_args.mli
index fbe0ec496..ab04ad0be 100644
--- a/src/client/embedded/bootstrap/client_proto_args.mli
+++ b/src/client/embedded/bootstrap/client_proto_args.mli
@@ -23,7 +23,7 @@ val force_arg: string * Arg.spec * string
 val endorsement_delay_arg: string * Arg.spec * string
 
 val tez_param :
-  n:string ->
+  name:string ->
   desc:string ->
   'a Cli_entries.params -> (Tez.t -> 'a) Cli_entries.params
 
diff --git a/src/client/embedded/bootstrap/client_proto_context.ml b/src/client/embedded/bootstrap/client_proto_context.ml
index ecffdecfb..fc48aab3b 100644
--- a/src/client/embedded/bootstrap/client_proto_context.ml
+++ b/src/client/embedded/bootstrap/client_proto_context.ml
@@ -34,8 +34,7 @@ let get_delegate_pkh = function
 
 let get_timestamp block () =
   Client_node_rpcs.Blocks.timestamp block >>= fun v ->
-  Cli_entries.message "%s" (Time.to_notation v) ;
-  Lwt.return ()
+  Cli_entries.message "%s" (Time.to_notation v)
 
 let list_contracts block () =
   Client_proto_rpcs.Context.Contract.list block >>=? fun contracts ->
@@ -58,7 +57,7 @@ let list_contracts block () =
       let kind = match Contract.is_default h with
         | Some _ -> " (default)"
         | None -> "" in
-      Cli_entries.message "%s%s%s" (Contract.to_b48check h) kind nm;
+      Cli_entries.message "%s%s%s" (Contract.to_b48check h) kind nm >>= fun () ->
       return ())
     contracts
 
@@ -75,15 +74,15 @@ let transfer block ?force
   Client_proto_rpcs.Context.Contract.counter block source >>=? fun pcounter ->
   let counter = Int32.succ pcounter in
   message "Acquired the source's sequence counter (%ld -> %ld)."
-    pcounter counter ;
+    pcounter counter >>= fun () ->
   Client_proto_rpcs.Helpers.Forge.Manager.transaction block
     ~net ~source ~sourcePubKey:src_pk ~counter ~amount
     ~destination ?parameters ~fee () >>=? fun bytes ->
-  message "Forged the raw transaction frame." ;
+  message "Forged the raw transaction frame." >>= fun () ->
   let signed_bytes = Ed25519.append_signature src_sk bytes in
   Client_node_rpcs.inject_operation ?force ~wait:true signed_bytes >>=? fun oph ->
-  answer "Operation successfully injected in the node." ;
-  answer "Operation hash is '%a'." Operation_hash.pp oph ;
+  answer "Operation successfully injected in the node." >>= fun () ->
+  answer "Operation hash is '%a'." Operation_hash.pp oph >>= fun () ->
   return ()
 
 let originate_account block ?force
@@ -93,16 +92,16 @@ let originate_account block ?force
   Client_proto_rpcs.Context.Contract.counter block source >>=? fun pcounter ->
   let counter = Int32.succ pcounter in
   message "Acquired the source's sequence counter (%ld -> %ld)."
-    pcounter counter ;
+    pcounter counter >>= fun () ->
   Client_proto_rpcs.Helpers.Forge.Manager.origination block
     ~net ~source ~sourcePubKey:src_pk ~managerPubKey:manager_pkh
     ~counter ~balance ?spendable
     ?delegatable ?delegatePubKey:delegate ~fee () >>=? fun (contract, bytes) ->
-  message "Forged the raw origination frame." ;
+  message "Forged the raw origination frame." >>= fun () ->
   let signed_bytes = Ed25519.append_signature src_sk bytes in
   Client_node_rpcs.inject_operation ?force ~wait:true signed_bytes >>=? fun oph ->
-  message "Operation successfully injected in the node." ;
-  message "Operation hash is '%a'." Operation_hash.pp oph ;
+  message "Operation successfully injected in the node." >>= fun () ->
+  message "Operation hash is '%a'." Operation_hash.pp oph >>= fun () ->
   return contract
 
 let originate_contract
@@ -115,18 +114,18 @@ let originate_contract
   Client_proto_rpcs.Context.Contract.counter block source >>=? fun pcounter ->
   let counter = Int32.succ pcounter in
   message "Acquired the source's sequence counter (%ld -> %ld)."
-    pcounter counter ;
+    pcounter counter >>= fun () ->
   Client_node_rpcs.Blocks.net block >>= fun net ->
   Client_proto_rpcs.Helpers.Forge.Manager.origination block
     ~net ~source ~sourcePubKey:src_pk ~managerPubKey:manager_pkh
     ~counter ~balance ~spendable:!spendable
     ?delegatable ?delegatePubKey
     ~script:(code, init) ~fee () >>=? fun (contract, bytes) ->
-  message "Forged the raw origination frame." ;
+  message "Forged the raw origination frame." >>= fun () ->
   let signed_bytes = Ed25519.append_signature src_sk bytes in
   Client_node_rpcs.inject_operation ?force ~wait:true signed_bytes >>=? fun oph ->
-  message "Operation successfully injected in the node." ;
-  message "Operation hash is '%a'." Operation_hash.pp oph ;
+  message "Operation successfully injected in the node." >>= fun () ->
+  message "Operation hash is '%a'." Operation_hash.pp oph >>= fun () ->
   return contract
 
 let commands () =
@@ -157,26 +156,24 @@ let commands () =
              Public_key_hash.add name pkh >>= fun () ->
              Public_key.add name pk >>= fun () ->
              Secret_key.add name sk >>= fun () ->
-             message "Bootstrap keys added under the name '%s'." name;
-             Lwt.return_unit)
+             message "Bootstrap keys added under the name '%s'." name)
            accounts >>= fun () ->
          Lwt.return_unit) ;
     command
       ~group: "context"
       ~desc: "get the balance of a contract"
       (prefixes [ "get" ; "balance" ]
-       @@ ContractAlias.destination_param ~n:"src" ~desc:"source contract"
+       @@ ContractAlias.destination_param ~name:"src" ~desc:"source contract"
        @@ stop)
       (fun (_, contract) () ->
          Client_proto_rpcs.Context.Contract.balance (block ()) contract
          >>= Client_proto_rpcs.handle_error >>= fun amount ->
-         answer "%a %s" Tez.pp amount tez_sym;
-         Lwt.return ());
+         answer "%a %s" Tez.pp amount tez_sym);
     command
       ~group: "context"
       ~desc: "get the manager of a block"
       (prefixes [ "get" ; "manager" ]
-       @@ ContractAlias.destination_param ~n:"src" ~desc:"source contract"
+       @@ ContractAlias.destination_param ~name:"src" ~desc:"source contract"
        @@ stop)
       (fun (_, contract) () ->
          Client_proto_rpcs.Context.Contract.manager (block ()) contract
@@ -184,8 +181,7 @@ let commands () =
          Public_key_hash.rev_find manager >>= fun mn ->
          Public_key_hash.to_source manager >>= fun m ->
          message "%s (%s)" m
-           (match mn with None -> "unknown" | Some n -> "known as " ^ n) ;
-         Lwt.return ());
+           (match mn with None -> "unknown" | Some n -> "known as " ^ n));
     command
       ~group: "context"
       ~desc: "open a new account"
@@ -193,16 +189,16 @@ let commands () =
               @ delegatable_args @ spendable_args)
       (prefixes [ "originate" ; "account" ]
        @@ RawContractAlias.fresh_alias_param
-         ~n: "new" ~desc: "name of the new contract"
+         ~name: "new" ~desc: "name of the new contract"
        @@ prefix "for"
        @@ Public_key_hash.alias_param
-         ~n: "mgr" ~desc: "manager of the new contract"
+         ~name: "mgr" ~desc: "manager of the new contract"
        @@ prefix "transfering"
        @@ tez_param
-         ~n: "qty" ~desc: "amount taken from source"
+         ~name: "qty" ~desc: "amount taken from source"
        @@ prefix "from"
        @@ ContractAlias.alias_param
-         ~n:"src" ~desc: "name of the source contract"
+         ~name:"src" ~desc: "name of the source contract"
        @@ stop)
       (fun neu (_, manager) balance (_, source) ->
          handle_error @@ fun () ->
@@ -210,7 +206,7 @@ let commands () =
          get_delegate_pkh !delegate >>= fun delegate ->
          Client_proto_contracts.get_manager (block ()) source >>=? fun src_pkh ->
          Client_keys.get_key src_pkh >>=? fun (src_name, src_pk, src_sk) ->
-         message "Got the source's manager keys (%s)." src_name ;
+         message "Got the source's manager keys (%s)." src_name >>= fun () ->
          originate_account (block ()) ~force:!force
            ~source ~src_pk ~src_sk ~manager_pkh:manager ~balance ~fee:!fee
            ~delegatable:!delegatable ~spendable:!spendable ?delegate:delegate
@@ -224,19 +220,19 @@ let commands () =
               delegatable_args @ spendable_args @ [ init_arg ])
       (prefixes [ "originate" ; "contract" ]
        @@ RawContractAlias.fresh_alias_param
-         ~n: "new" ~desc: "name of the new contract"
+         ~name: "new" ~desc: "name of the new contract"
        @@ prefix "for"
        @@ Public_key_hash.alias_param
-         ~n: "mgr" ~desc: "manager of the new contract"
+         ~name: "mgr" ~desc: "manager of the new contract"
        @@ prefix "transfering"
        @@ tez_param
-         ~n: "qty" ~desc: "amount taken from source"
+         ~name: "qty" ~desc: "amount taken from source"
        @@ prefix "from"
        @@ ContractAlias.alias_param
-         ~n:"src" ~desc: "name of the source contract"
+         ~name:"src" ~desc: "name of the source contract"
        @@ prefix "running"
        @@ Program.source_param
-         ~n:"prg" ~desc: "script of the account\n\
+         ~name:"prg" ~desc: "script of the account\n\
                           combine with -init if the storage type is non void"
        @@ stop)
       (fun neu (_, manager) balance (_, source) code ->
@@ -245,7 +241,7 @@ let commands () =
          get_delegate_pkh !delegate >>= fun delegate ->
          Client_proto_contracts.get_manager (block ()) source >>=? fun src_pkh ->
          Client_keys.get_key src_pkh >>=? fun (src_name, src_pk, src_sk) ->
-         message "Got the source's manager keys (%s)." src_name ;
+         message "Got the source's manager keys (%s)." src_name >>= fun () ->
          originate_contract (block ()) ~force:!force
            ~source ~src_pk ~src_sk ~manager_pkh:manager ~balance ~fee:!fee
            ~delegatable:!delegatable ?delegatePubKey:delegate ~code ~init:!init ()
@@ -258,19 +254,19 @@ let commands () =
       ~args: [ fee_arg ; arg_arg ; force_arg ]
       (prefixes [ "transfer" ]
        @@ tez_param
-         ~n: "qty" ~desc: "amount taken from source"
+         ~name: "qty" ~desc: "amount taken from source"
        @@ prefix "from"
        @@ ContractAlias.alias_param
-         ~n: "src" ~desc: "name of the source contract"
+         ~name: "src" ~desc: "name of the source contract"
        @@ prefix "to"
        @@ ContractAlias.destination_param
-         ~n: "dst" ~desc: "name/literal of the destination contract"
+         ~name: "dst" ~desc: "name/literal of the destination contract"
        @@ stop)
       (fun amount (_, source) (_, destination) ->
          handle_error @@ fun () ->
          Client_proto_contracts.get_manager (block ()) source >>=? fun src_pkh ->
          Client_keys.get_key src_pkh >>=? fun (src_name, src_pk, src_sk) ->
-         message "Got the source's manager keys (%s)." src_name ;
+         message "Got the source's manager keys (%s)." src_name >>= fun () ->
          transfer (block ()) ~force:!force
            ~source ~src_pk ~src_sk ~destination ?arg:!arg ~amount ~fee:!fee ())
   ]
diff --git a/src/client/embedded/bootstrap/client_proto_contracts.ml b/src/client/embedded/bootstrap/client_proto_contracts.ml
index 9a921f594..d48d540e9 100644
--- a/src/client/embedded/bootstrap/client_proto_contracts.ml
+++ b/src/client/embedded/bootstrap/client_proto_contracts.ml
@@ -51,33 +51,34 @@ module ContractAlias = struct
         find_key key
     | _ -> find s
 
-  let alias_param ?(n = "name") ?(desc = "existing contract alias") next =
-    Cli_entries.Param
-      (n, desc ^ "\n"
-          ^ "can be an contract alias or a key alias (autodetected in this order)\n\
-             use 'key:name' to force the later", get_contract, next)
+  let alias_param ?(name = "name") ?(desc = "existing contract alias") next =
+    let desc =
+      desc ^ "\n"
+      ^ "can be an contract alias or a key alias (autodetected in this order)\n\
+         use 'key:name' to force the later" in
+    Cli_entries.param ~name ~desc get_contract next
 
-   let destination_param ?(n = "dst") ?(desc = "destination contract") next =
-     Cli_entries.Param
-       (n,
-        desc ^ "\n"
-        ^ "can be an alias, a key alias, or a litteral (autodetected in this order)\n\
-           use 'text:litteral', 'alias:name', 'key:name' to force",
-        (fun s ->
-           match Utils.split ~limit:1 ':' s with
-           | [ "alias" ; alias ]->
-               find alias
-           | [ "key" ; text ] ->
-               Client_keys.Public_key_hash.find text >>= fun v ->
-               Lwt.return (s, Contract.default_contract v)
-           | _ ->
-               Lwt.catch
-                 (fun () -> find s)
-                 (fun _ ->
-                    match Contract.of_b48check s with
-                    | Error _ -> Lwt.fail (Failure "bad contract notation")
-                    | Ok v -> Lwt.return (s, v))),
-        next)
+  let destination_param ?(name = "dst") ?(desc = "destination contract") next =
+    let desc =
+      desc ^ "\n"
+      ^ "can be an alias, a key alias, or a litteral (autodetected in this order)\n\
+         use 'text:litteral', 'alias:name', 'key:name' to force" in
+    Cli_entries.param ~name ~desc
+      (fun s ->
+         match Utils.split ~limit:1 ':' s with
+         | [ "alias" ; alias ]->
+             find alias
+         | [ "key" ; text ] ->
+             Client_keys.Public_key_hash.find text >>= fun v ->
+             Lwt.return (s, Contract.default_contract v)
+         | _ ->
+             Lwt.catch
+               (fun () -> find s)
+               (fun _ ->
+                  match Contract.of_b48check s with
+                  | Error _ -> Lwt.fail (Failure "bad contract notation")
+                  | Ok v -> Lwt.return (s, v)))
+      next
 
    let name contract =
      rev_find contract >|= function
@@ -150,17 +151,16 @@ let commands  () =
       (fixed [ "list" ; "known" ; "contracts" ])
       (fun () ->
          RawContractAlias.load () >>= fun list ->
-         List.iter (fun (n, v) ->
+         Lwt_list.iter_s (fun (n, v) ->
              let v = Contract.to_b48check v in
              message "%s: %s" n v)
-           list ;
+           list >>= fun () ->
          Client_keys.Public_key_hash.load () >>= fun list ->
          Lwt_list.iter_s (fun (n, v) ->
              RawContractAlias.mem n >>= fun mem ->
              let p = if mem then "key:" else "" in
              let v = Contract.to_b48check (Contract.default_contract v) in
-             message "%s%s: %s" p n v ;
-             Lwt.return_unit)
+             message "%s%s: %s" p n v)
            list >>= fun () ->
          Lwt.return ()) ;
     command
diff --git a/src/client/embedded/bootstrap/client_proto_contracts.mli b/src/client/embedded/bootstrap/client_proto_contracts.mli
index 87e40ba04..54257e48f 100644
--- a/src/client/embedded/bootstrap/client_proto_contracts.mli
+++ b/src/client/embedded/bootstrap/client_proto_contracts.mli
@@ -13,12 +13,12 @@ module RawContractAlias :
 module ContractAlias : sig
   val get_contract: string -> (string * Contract.t) Lwt.t
   val alias_param:
-    ?n:string ->
+    ?name:string ->
     ?desc:string ->
     'a Cli_entries.params ->
     (Lwt_io.file_name * Contract.t -> 'a) Cli_entries.params
   val destination_param:
-    ?n:string ->
+    ?name:string ->
     ?desc:string ->
     'a Cli_entries.params ->
     (Lwt_io.file_name * Contract.t -> 'a) Cli_entries.params
diff --git a/src/client/embedded/bootstrap/client_proto_programs.ml b/src/client/embedded/bootstrap/client_proto_programs.ml
index 5620b123d..a7cabf824 100644
--- a/src/client/embedded/bootstrap/client_proto_programs.ml
+++ b/src/client/embedded/bootstrap/client_proto_programs.ml
@@ -183,7 +183,7 @@ let commands () =
       ~desc: "lists all known programs"
       (fixed [ "list" ; "known" ; "programs" ])
       (fun () -> Program.load () >>= fun list ->
-        List.iter (fun (n, _) -> message "%s" n) list ; Lwt.return ()) ;
+        Lwt_list.iter_s (fun (n, _) -> message "%s" n) list) ;
     command
       ~group: "programs"
       ~desc: "remember a program under some name"
@@ -262,7 +262,7 @@ let commands () =
          Client_proto_rpcs.Helpers.typecheck_code (block ()) program >>= function
          | Ok type_map ->
              let type_map, program = unexpand_macros type_map program in
-             message "Well typed" ;
+             message "Well typed" >>= fun () ->
              if !show_types then begin
                print_program
                  (fun l -> List.mem_assoc l type_map)
@@ -296,8 +296,7 @@ let commands () =
          Client_proto_rpcs.Helpers.typecheck_untagged_data
            (block ()) (data, exp_ty) >>= function
          | Ok () ->
-             message "Well typed" ;
-             Lwt.return ()
+             message "Well typed"
          | Error errs ->
              pp_print_error Format.err_formatter errs ;
              error "ill-typed data") ;
@@ -312,8 +311,7 @@ let commands () =
          let open Data_encoding in
          Client_proto_rpcs.Helpers.hash_data (block ()) data >>= function
          | Ok hash ->
-             message "%S" hash;
-             Lwt.return ()
+             message "%S" hash
          | Error errs ->
              pp_print_error Format.err_formatter errs ;
              error "ill-formed data") ;
@@ -337,8 +335,7 @@ let commands () =
                hash
                (signature |>
                 Data_encoding.Binary.to_bytes Ed25519.signature_encoding |>
-                Hex_encode.hex_of_bytes) ;
-             Lwt.return ()
+                Hex_encode.hex_of_bytes)
          | Error errs ->
              pp_print_error Format.err_formatter errs ;
              error "ill-formed data") ;
diff --git a/src/client/embedded/bootstrap/mining/client_mining_main.ml b/src/client/embedded/bootstrap/mining/client_mining_main.ml
index e87c68216..9e8c33156 100644
--- a/src/client/embedded/bootstrap/mining/client_mining_main.ml
+++ b/src/client/embedded/bootstrap/mining/client_mining_main.ml
@@ -101,7 +101,7 @@ let reveal_nonces ?force () =
 
 open Client_proto_args
 
-let run_daemon delegates =
+let run_daemon delegates () =
   Client_mining_daemon.run
     ?max_priority:!max_priority
     ~delay:!endorsement_delay
@@ -126,7 +126,7 @@ let commands () =
       ~args: [ force_arg ]
       (prefixes [ "endorse"; "for" ]
        @@ Client_keys.Public_key_hash.alias_param
-         ~n:"miner" ~desc: "name of the delegate owning the endorsement right"
+         ~name:"miner" ~desc: "name of the delegate owning the endorsement right"
        @@ stop)
       (fun (_, delegate) () ->
          endorse_block
@@ -138,7 +138,7 @@ let commands () =
       ~args: [ max_priority_arg ; force_arg ]
       (prefixes [ "mine"; "for" ]
        @@ Client_keys.Public_key_hash.alias_param
-         ~n:"miner" ~desc: "name of the delegate owning the mining right"
+         ~name:"miner" ~desc: "name of the delegate owning the mining right"
        @@ stop)
       (fun (_, delegate) () ->
          mine_block (block ())
@@ -150,7 +150,7 @@ let commands () =
       ~args: [ force_arg ]
       (prefixes [ "reveal"; "nonce"; "for" ]
        @@ Cli_entries.seq_of_param Block_hash.param)
-      (fun block_hashes ->
+      (fun block_hashes () ->
          reveal_block_nonces ~force:!force block_hashes >>= Client_proto_rpcs.handle_error) ;
     command
       ~group: "delegate"
diff --git a/src/client_main.ml b/src/client_main.ml
index e57cdd9cf..11d278621 100644
--- a/src/client_main.ml
+++ b/src/client_main.ml
@@ -11,6 +11,27 @@
 
 open Lwt
 
+let () =
+  let startup =
+    CalendarLib.Printer.Precise_Calendar.sprint
+      "%Y-%m-%dT%H:%M:%SZ"
+      (CalendarLib.Calendar.Precise.now ()) in
+  let log channel msg = match channel with
+    | "stdout" ->
+        print_endline msg ;
+        Lwt.return ()
+    | "stderr" ->
+        prerr_endline msg ;
+        Lwt.return ()
+    | log ->
+        Utils.create_dir Client_config.(base_dir#get // "logs" // log) >>= fun () ->
+        Lwt_io.with_file
+          ~flags: Unix.[ O_APPEND ; O_CREAT ; O_WRONLY ]
+          ~mode: Lwt_io.Output
+          Client_config.(base_dir#get // "logs" // log // startup)
+          (fun chan -> Lwt_io.write chan msg) in
+  Cli_entries.log_hook := Some log
+
 (* Main (lwt) entry *)
 let main () =
   Random.self_init () ;
@@ -24,7 +45,7 @@ let main () =
          (fun _ ->
             Cli_entries.message "\n\
                                  The connection to the RPC server failed, \
-                                 using the default protocol version.\n" ;
+                                 using the default protocol version.\n" >>= fun () ->
             Lwt.return Client_bootstrap.Client_proto_main.protocol)
        >>= fun version ->
        let commands =
@@ -35,7 +56,7 @@ let main () =
          Client_version.commands_for_version version in
        Client_config.parse_args ~version
          (Cli_entries.usage commands)
-         (Cli_entries.inline_dispatcher commands))
+         (Cli_entries.inline_dispatch commands))
     (function
       | Arg.Help help ->
           Format.printf "%s%!" help ;
diff --git a/src/utils/cli_entries.ml b/src/utils/cli_entries.ml
index 3e262b0a6..c7071af56 100644
--- a/src/utils/cli_entries.ml
+++ b/src/utils/cli_entries.ml
@@ -16,21 +16,30 @@ exception Command_not_found
 exception Bad_argument of int * string * string
 exception Command_failed of string
 
-(* A simple structure for command interpreters. *)
-type 'a params =
-  | Prefix : string * 'a params -> 'a params
-  | Param : string * string * (string -> 'p Lwt.t) * 'a params -> ('p -> 'a) params
-  | Stop : (unit -> unit Lwt.t) params
-  | More : (string list -> unit Lwt.t) params
-  | Seq : string * string * (string -> 'p Lwt.t) -> ('p list -> unit Lwt.t) params
+(* A simple structure for command interpreters.
+   This is more generic than the exported one, see end of file. *)
+type ('a, 'arg, 'ret) tparams =
+  | Prefix : string * ('a, 'arg, 'ret) tparams ->
+    ('a, 'arg, 'ret) tparams
+  | Param : string * string *
+            (string -> 'p Lwt.t) *
+            ('a, 'arg, 'ret) tparams ->
+    ('p -> 'a, 'arg, 'ret) tparams
+  | Stop :
+      ('arg -> 'ret Lwt.t, 'arg, 'ret) tparams
+  | More :
+      (string list -> 'arg -> 'ret Lwt.t, 'arg, 'ret) tparams
+  | Seq : string * string *
+          (string -> 'p Lwt.t) ->
+    ('p list -> 'arg -> 'ret Lwt.t, 'arg, 'ret) tparams
 
 (* A command wraps a callback with its type and info *)
-and command =
+and ('arg, 'ret) tcommand =
   | Command
-    : 'a params * 'a *
+    : ('a, 'arg, 'ret) tparams * 'a *
       desc option * tag list * group option *
       (Arg.key * Arg.spec * Arg.doc) list
-    -> command
+    -> ('arg, 'ret) tcommand
 
 and desc = string
 and group = string
@@ -77,25 +86,15 @@ let command ?desc ?(tags = []) ?group ?(args = []) params cb =
 (* Param combinators *)
 let string n desc next = param n desc (fun s -> return s) next
 
-(* Error combinators for use in commands *)
-let kasprintf cont fmt =
-  let buffer = Buffer.create 100 in
-  let ppf = Format.formatter_of_buffer buffer in
-  Format.kfprintf (fun ppf ->
-      Format.fprintf ppf "%!";
-      cont (Buffer.contents buffer))
-    ppf fmt
-let error fmt = kasprintf (fun msg -> Lwt.fail (Command_failed msg)) fmt
-let message fmt = kasprintf (Format.eprintf "%s\n%!") fmt
-let answer fmt = kasprintf (Format.printf "%s\n%!") fmt
-let param_error fmt = kasprintf (fun msg -> Lwt.fail (Failure msg)) fmt
-
 (* Command execution *)
-let exec (Command (params, cb, _, _, _, _)) args =
+let exec
+    (type arg) (type ret)
+    (Command (params, cb, _, _, _, _)) (last : arg) args =
   let rec exec
-    : type a. int -> a params -> a -> string list -> unit Lwt.t = fun i params cb args ->
+    : type a. int -> (a, arg, ret) tparams -> a -> string list -> ret Lwt.t
+    = fun i params cb args ->
     match params, args with
-    | Stop, [] -> cb ()
+    | Stop, [] -> cb last
     | Stop, _ -> Lwt.fail Command_not_found
     | Seq (_, _, f), seq ->
         let rec do_seq i acc = function
@@ -108,8 +107,8 @@ let exec (Command (params, cb, _, _, _, _)) args =
                   | exn -> Lwt.fail exn) >>= fun v ->
               do_seq (succ i) (v :: acc) rest in
         do_seq i [] seq >>= fun parsed ->
-        cb parsed
-    | More, rest -> cb rest
+        cb parsed last
+    | More, rest -> cb rest last
     | Prefix (n, next), p :: rest when n = p ->
         exec (succ i) next cb rest
     | Param (_, _, f, next), p :: rest ->
@@ -122,116 +121,125 @@ let exec (Command (params, cb, _, _, _, _)) args =
     | _ -> Lwt.fail Command_not_found
   in exec 1 params cb args
 
-module Command_tree = struct
-  type level =
-    { stop : command option ;
-      prefix : (string * tree) list }
-  and param_level =
-    { stop : command option ;
-      tree : tree }
-  and tree =
-    | TPrefix of level
-    | TParam of param_level
-    | TStop of command
-    | TMore of command
-    | TEmpty
-  let insert root (Command (params, _, _, _, _, _) as command) =
-    let rec insert_tree
-      : type a. tree -> a params -> tree
-      = fun t c -> match t, c with
-        | TEmpty, Stop -> TStop command
-        | TEmpty, More -> TMore command
-        | TEmpty, Seq _ -> TMore command
-        | TEmpty, Param (_, _, _, next) ->
-            TParam { tree = insert_tree TEmpty next ; stop = None }
-        | TEmpty, Prefix (n, next) ->
-            TPrefix { stop = None ; prefix = [ (n, insert_tree TEmpty next) ] }
-        | TStop command, Param (_, _, _, next) ->
-            TParam { tree = insert_tree TEmpty next ; stop = Some command }
-        | TStop command, Prefix (n, next) ->
-            TPrefix { stop = Some command ;
-                      prefix = [ (n, insert_tree TEmpty next) ] }
-        | TParam t, Param (_, _, _, next) ->
-            TParam { t with tree = insert_tree t.tree next }
-        | TPrefix ({ prefix } as l), Prefix (n, next) ->
-            let rec insert_prefix = function
-              | [] -> [ (n, insert_tree TEmpty next) ]
-              | (n', t) :: rest when n = n' -> (n, insert_tree t next) :: rest
-              | item :: rest -> item :: insert_prefix rest in
-            TPrefix { l with prefix = insert_prefix prefix }
-        | TPrefix ({ stop = None } as l), Stop ->
-            TPrefix { l with stop = Some command }
-        | TParam ({ stop = None } as l), Stop ->
-            TParam { l with stop = Some command }
-        | _, _ ->
-            Pervasives.failwith
-              "Cli_entries.Command_tree.insert: conflicting commands" in
-    insert_tree root params
-  let make commands =
-    List.fold_left insert TEmpty commands
-  let dispatcher tree args =
-    let rec loop = function
-      | TStop c, [] -> exec c args
-      | TPrefix { stop = Some c }, [] -> exec c args
-      | TMore c, _ -> exec c args
-      | TPrefix { prefix }, n :: rest ->
-          begin try
-              let t = List.assoc n prefix in
-              loop (t, rest)
-            with Not_found -> Lwt.fail Command_not_found end
-      | TParam { tree }, _ :: rest ->
-          loop (tree, rest)
-      | _, _ -> Lwt.fail Command_not_found
-    in
-    loop (tree, args)
-  let inline_dispatcher tree () =
-    let state = ref (tree, []) in
-    fun arg -> match !state, arg with
-      | (( TStop c |
-           TMore c |
-           TPrefix { stop = Some c } |
-           TParam { stop = Some c}), acc),
-        `End ->
-          state := (TEmpty, []) ;
-          `Res (exec c (List.rev acc))
-      | (TMore c, acc), `Arg n ->
-          state := (TMore c, n :: acc) ;
-          `Nop
-      | (TPrefix { prefix }, acc), `Arg n ->
-          begin try
-              let t = List.assoc n prefix in
-              state := (t, n :: acc) ;
-              begin match t with
-                | TStop (Command (_, _, _, _, _, args))
-                | TMore (Command (_, _, _, _, _, args)) -> `Args args
-                | _ -> `Nop end
-            with Not_found -> `Fail Command_not_found end
-      | (TParam { tree }, acc), `Arg n ->
-          state := (tree, n :: acc) ;
-          begin match tree with
-            | TStop (Command (_, _, _, _, _, args))
-            | TMore (Command (_, _, _, _, _, args)) -> `Args args
-            | _ -> `Nop end
-      | _, _ -> `Fail Command_not_found
-end
+(* Command dispatch tree *)
+type ('arg, 'ret) level =
+  { stop : ('arg, 'ret) tcommand option ;
+    prefix : (string * ('arg, 'ret) tree) list }
+and ('arg, 'ret) param_level =
+  { stop : ('arg, 'ret) tcommand option ;
+    tree : ('arg, 'ret) tree }
+and ('arg, 'ret) tree =
+  | TPrefix of ('arg, 'ret) level
+  | TParam of ('arg, 'ret) param_level
+  | TStop of ('arg, 'ret) tcommand
+  | TMore of ('arg, 'ret) tcommand
+  | TEmpty
+
+let insert_in_dispatch_tree
+    (type arg) (type ret)
+    root (Command (params, _, _, _, _, _) as command) =
+  let rec insert_tree
+    : type a. (arg, ret) tree -> (a, arg, ret) tparams -> (arg, ret) tree
+    = fun t c -> match t, c with
+      | TEmpty, Stop -> TStop command
+      | TEmpty, More -> TMore command
+      | TEmpty, Seq _ -> TMore command
+      | TEmpty, Param (_, _, _, next) ->
+          TParam { tree = insert_tree TEmpty next ; stop = None }
+      | TEmpty, Prefix (n, next) ->
+          TPrefix { stop = None ; prefix = [ (n, insert_tree TEmpty next) ] }
+      | TStop command, Param (_, _, _, next) ->
+          TParam { tree = insert_tree TEmpty next ; stop = Some command }
+      | TStop command, Prefix (n, next) ->
+          TPrefix { stop = Some command ;
+                    prefix = [ (n, insert_tree TEmpty next) ] }
+      | TParam t, Param (_, _, _, next) ->
+          TParam { t with tree = insert_tree t.tree next }
+      | TPrefix ({ prefix } as l), Prefix (n, next) ->
+          let rec insert_prefix = function
+            | [] -> [ (n, insert_tree TEmpty next) ]
+            | (n', t) :: rest when n = n' -> (n, insert_tree t next) :: rest
+            | item :: rest -> item :: insert_prefix rest in
+          TPrefix { l with prefix = insert_prefix prefix }
+      | TPrefix ({ stop = None } as l), Stop ->
+          TPrefix { l with stop = Some command }
+      | TParam ({ stop = None } as l), Stop ->
+          TParam { l with stop = Some command }
+      | _, _ ->
+          Pervasives.failwith
+            "Cli_entries.Command_tree.insert: conflicting commands" in
+  insert_tree root params
+
+let make_dispatch_tree commands =
+  List.fold_left insert_in_dispatch_tree TEmpty commands
+
+let tree_dispatch tree last args =
+  let rec loop = function
+    | TStop c, [] -> exec c last args
+    | TPrefix { stop = Some c }, [] -> exec c last args
+    | TMore c, _ -> exec c last args
+    | TPrefix { prefix }, n :: rest ->
+        begin try
+            let t = List.assoc n prefix in
+            loop (t, rest)
+          with Not_found -> Lwt.fail Command_not_found end
+    | TParam { tree }, _ :: rest ->
+        loop (tree, rest)
+    | _, _ -> Lwt.fail Command_not_found
+  in
+  loop (tree, args)
+
+let inline_tree_dispatch tree last =
+  let state = ref (tree, []) in
+  fun arg -> match !state, arg with
+    | (( TStop c |
+         TMore c |
+         TPrefix { stop = Some c } |
+         TParam { stop = Some c}), acc),
+      `End ->
+        state := (TEmpty, []) ;
+        `Res (exec c last (List.rev acc))
+    | (TMore c, acc), `Arg n ->
+        state := (TMore c, n :: acc) ;
+        `Nop
+    | (TPrefix { prefix }, acc), `Arg n ->
+        begin try
+            let t = List.assoc n prefix in
+            state := (t, n :: acc) ;
+            begin match t with
+              | TStop (Command (_, _, _, _, _, args))
+              | TMore (Command (_, _, _, _, _, args)) -> `Args args
+              | _ -> `Nop end
+          with Not_found -> `Fail Command_not_found end
+    | (TParam { tree }, acc), `Arg n ->
+        state := (tree, n :: acc) ;
+        begin match tree with
+          | TStop (Command (_, _, _, _, _, args))
+          | TMore (Command (_, _, _, _, _, args)) -> `Args args
+          | _ -> `Nop end
+    | _, _ -> `Fail Command_not_found
 
 (* Try a list of commands on a list of arguments *)
-let dispatcher commands =
-  let tree = Command_tree.make commands in
-  fun args -> Command_tree.dispatcher tree args
+let dispatch commands =
+  let tree = make_dispatch_tree commands in
+  tree_dispatch tree
 
 (* Argument-by-argument dispatcher to be used during argument parsing *)
-let inline_dispatcher commands =
-  let tree = Command_tree.make commands in
-  Command_tree.inline_dispatcher tree
+let inline_dispatch commands =
+  let tree = make_dispatch_tree commands in
+  inline_tree_dispatch tree
 
 (* Command line help for a set of commands *)
-let usage commands options =
+let usage
+      (type arg) (type ret)
+      commands options =
   let trim s = (* config-file wokaround *)
     Utils.split '\n' s |>
     List.map String.trim |>
     String.concat "\n" in
-  let rec help : type a. Format.formatter -> a params -> unit = fun ppf -> function
+  let rec help
+    : type a. Format.formatter -> (a, arg, ret) tparams -> unit
+    = fun ppf -> function
     | Stop -> ()
     | More -> Format.fprintf ppf "..."
     | Seq (n, "", _) -> Format.fprintf ppf "[ (%s) ...]" n
@@ -242,7 +250,9 @@ let usage commands options =
     | Prefix (n, next) -> Format.fprintf ppf "%s %a" n help next
     | Param (n, "", _, next) -> Format.fprintf ppf "(%s) %a" n help next
     | Param (_, desc, _, next) -> Format.fprintf ppf "(%s) %a" desc help next in
-  let rec help_sum : type a. Format.formatter -> a params -> unit = fun ppf -> function
+  let rec help_sum
+    : type a. Format.formatter -> (a, arg, ret) tparams -> unit
+    = fun ppf -> function
     | Stop -> ()
     | More -> Format.fprintf ppf "..."
     | Seq (n, _, _) -> Format.fprintf ppf "[ (%s) ... ]" n
@@ -250,13 +260,21 @@ let usage commands options =
     | Param (n, _, _, Stop) -> Format.fprintf ppf "(%s)" n
     | Prefix (n, next) -> Format.fprintf ppf "%s %a" n help_sum next
     | Param (n, _, _, next) -> Format.fprintf ppf "(%s) %a" n help_sum next in
-  let rec help_args : type a. Format.formatter -> a params -> unit = fun ppf -> function
-    | Stop -> ()
-    | More -> Format.fprintf ppf "..."
-    | Seq (n, desc, _) -> Format.fprintf ppf "(%s): @[<hov>%a@]" n Format.pp_print_text (trim desc)
-    | Prefix (_, next) -> help_args ppf next
-    | Param (n, desc, _, Stop) -> Format.fprintf ppf "(%s): @[<hov>%a@]" n Format.pp_print_text (trim desc)
-    | Param (n, desc, _, next) -> Format.fprintf ppf "(%s): @[<hov>%a@]@,%a" n Format.pp_print_text (trim desc) help_args next in
+  let rec help_args
+    : type a. Format.formatter -> (a, arg, ret) tparams -> unit
+    = fun ppf -> function
+      | Stop -> ()
+      | More -> Format.fprintf ppf "..."
+      | Seq (n, desc, _) ->
+          Format.fprintf ppf "(%s): @[<hov>%a@]"
+            n Format.pp_print_text (trim desc)
+      | Prefix (_, next) -> help_args ppf next
+      | Param (n, desc, _, Stop) ->
+          Format.fprintf ppf "(%s): @[<hov>%a@]"
+            n Format.pp_print_text (trim desc)
+      | Param (n, desc, _, next) ->
+          Format.fprintf ppf "(%s): @[<hov>%a@]@,%a"
+            n Format.pp_print_text (trim desc) help_args next in
   let option_help ppf (n, opt, desc) =
     Format.fprintf ppf "%s%s" n
       Arg.(let rec example opt = match opt with
@@ -277,27 +295,38 @@ let usage commands options =
       Format.fprintf ppf "@,  @[<hov>%a@]" Format.pp_print_text (trim desc) in
   let command_help ppf (Command (p, _, desc, _, _, options)) =
     let small = Format.asprintf "@[<h>%a@]" help p in
+    let desc =
+      match desc with
+      | None -> "undocumented command"
+      | Some desc -> trim desc in
     if String.length small < 50 then begin
       Format.fprintf ppf "@[<v 2>%s@,@[<hov>%a@]"
-        small
-        Format.pp_print_text (match desc with None -> "undocumented command" | Some desc -> trim desc)
+        small Format.pp_print_text desc
     end else begin
       Format.fprintf ppf "@[<v 2>%a@,@[<hov 0>%a@]@,%a"
         help_sum p
-        Format.pp_print_text (match desc with None -> "undocumented command" | Some desc -> trim desc)
+        Format.pp_print_text desc
         help_args p ;
     end ;
     if options = [] then
       Format.fprintf ppf "@]"
     else
-      Format.fprintf ppf "@,%a@]" (Format.pp_print_list option_help) options in
+      Format.fprintf ppf "@,%a@]"
+        (Format.pp_print_list option_help)
+        options in
   let rec group_help ppf (n, commands) =
+    let title =
+      match n with
+      | None -> "Miscellaneous commands"
+      | Some n -> group_title n in
     Format.fprintf ppf "@[<v 2>%s:@,%a@]"
-      (match n with None -> "Miscellaneous commands" | Some n -> group_title n)
+      title
       (Format.pp_print_list command_help) !commands in
   let usage ppf (by_group, options) =
     Format.fprintf ppf
-      "@[<v>@[<v 2>Usage:@,%s [ options ] command [ command options ]@]@,@[<v 2>Options:@,%a@]@,%a@]"
+      "@[<v>@[<v 2>Usage:@,%s [ options ] command [ command options ]@]@,\
+       @[<v 2>Options:@,%a@]@,\
+       %a@]"
       Sys.argv.(0)
       (Format.pp_print_list option_help) options
       (Format.pp_print_list group_help) by_group in
@@ -312,3 +341,34 @@ let usage commands options =
            (g, ref [ c ]) :: acc)
       [] commands |> List.sort compare in
   Format.asprintf "%a" usage (by_group, options)
+
+(* Pre-instanciated types *)
+type 'a params = ('a, unit, unit) tparams
+type command = (unit, unit) tcommand
+
+let log_hook
+  : (string -> string -> unit Lwt.t) option ref
+  = ref None
+
+let log channel msg =
+  match !log_hook with
+  | None -> Lwt.fail (Invalid_argument "Cli_entries.log: uninitialized hook")
+  | Some hook -> hook channel msg
+
+let error fmt=
+  Format.kasprintf
+    (fun msg ->
+       Lwt.fail (Failure msg))
+    fmt
+
+let message fmt =
+  Format.kasprintf
+    (fun msg -> log "stdout" msg)
+    fmt
+
+let answer = message
+
+let log name fmt =
+  Format.kasprintf
+    (fun msg -> log name msg)
+    fmt
diff --git a/src/utils/cli_entries.mli b/src/utils/cli_entries.mli
index 7d6e63bde..209289a3b 100644
--- a/src/utils/cli_entries.mli
+++ b/src/utils/cli_entries.mli
@@ -14,29 +14,13 @@ exception Command_not_found
 exception Bad_argument of int * string * string
 exception Command_failed of string
 
-type 'a params =
-  | Prefix: string * 'a params -> 'a params
-  | Param: string * string * (string -> 'p Lwt.t) * 'a params -> ('p -> 'a) params
-  | Stop: (unit -> unit Lwt.t) params
-  | More: (string list -> unit Lwt.t) params
-  | Seq : string * string * (string -> 'p Lwt.t) -> ('p list -> unit Lwt.t) params
-
-and command =
-  | Command
-    : 'a params * 'a *
-      desc option * tag list * group option *
-      (Arg.key * Arg.spec * Arg.doc) list
-    -> command
+type 'a params
+type command
 
 and desc = string
 and group = string
 and tag = string
 
-val error: ('a, Format.formatter, unit, 'b Lwt.t) format4 -> 'a
-val param_error: ('a, Format.formatter, unit, 'b Lwt.t) format4 -> 'a
-val message: ('a, Format.formatter, unit, unit) format4 -> 'a
-val answer: ('a, Format.formatter, unit, unit) format4 -> 'a
-
 val param:
   name: string ->
   desc: string ->
@@ -49,12 +33,13 @@ val stop: (unit -> unit Lwt.t) params
 val seq:
   name: string ->
   desc: string ->
-  (string -> 'p Lwt.t) -> ('p list -> unit Lwt.t) params
+  (string -> 'p Lwt.t) ->
+  ('p list -> unit -> unit Lwt.t) params
 
-(* [seq_of_param (param ~name ~desc f) = seq ~name ~desc f] *)
 val seq_of_param:
-  ((unit -> unit Lwt.t) params -> ('a -> unit -> unit Lwt.t) params) ->
-  ('a list -> unit Lwt.t) params
+  ((unit -> unit Lwt.t) params ->
+   ('a -> unit -> unit Lwt.t) params) ->
+  ('a list -> unit -> unit Lwt.t) params
 
 val command:
   ?desc:desc ->
@@ -68,7 +53,7 @@ val register_tag: tag -> string -> unit
 
 val usage:
   command list -> (string * Arg.spec * string) list -> string
-val inline_dispatcher:
+val inline_dispatch:
   command list ->
   unit ->
   [> `Arg of string | `End ] ->
@@ -76,3 +61,13 @@ val inline_dispatcher:
   | `Fail of exn
   | `Nop
   | `Res of unit Lwt.t ]
+
+val dispatch:
+  command list -> unit -> string list -> unit Lwt.t
+
+val log_hook : (string -> string -> unit Lwt.t) option ref
+
+val error : ('a, Format.formatter, unit, 'b Lwt.t) format4 -> 'a
+val message : ('a, Format.formatter, unit, unit Lwt.t) format4 -> 'a
+val answer : ('a, Format.formatter, unit, unit Lwt.t) format4 -> 'a
+val log : string -> ('a, Format.formatter, unit, unit Lwt.t) format4 -> 'a