diff --git a/src/lib_base/p2p_peer_id.ml b/src/lib_base/p2p_peer_id.ml
index 7dfb5e1df..31083d907 100644
--- a/src/lib_base/p2p_peer_id.ml
+++ b/src/lib_base/p2p_peer_id.ml
@@ -9,3 +9,9 @@
 
 include Crypto_box.Public_key_hash
 
+let rpc_arg =
+  RPC_arg.like
+    rpc_arg
+    ~descr:"A cryptographic node identity (Base58Check-encoded)"
+    "peer_id"
+
diff --git a/src/lib_crypto/block_hash.ml b/src/lib_crypto/block_hash.ml
index 85bca9c64..5c0984ce2 100644
--- a/src/lib_crypto/block_hash.ml
+++ b/src/lib_crypto/block_hash.ml
@@ -8,8 +8,8 @@
 (**************************************************************************)
 
 include Blake2B.Make (Base58) (struct
-    let name = "Block_hash"
-    let title = "A Tezos block ID"
+    let name = "block_hash"
+    let title = "A block identifier"
     let b58check_prefix = Base58.Prefix.block_hash
     let size = None
   end)
diff --git a/src/lib_crypto/signature.ml b/src/lib_crypto/signature.ml
index fb53e0e90..ecded70d8 100644
--- a/src/lib_crypto/signature.ml
+++ b/src/lib_crypto/signature.ml
@@ -165,6 +165,12 @@ module Public_key_hash = struct
       let encoding = encoding
     end)
 
+  let rpc_arg =
+    RPC_arg.like
+      rpc_arg
+      ~descr:"A Secp256k1 of a Ed25519 public key hash (Base58Check-encoded)"
+      "pkh"
+
 end
 
 module Public_key = struct
diff --git a/src/lib_shell_services/worker_services.ml b/src/lib_shell_services/worker_services.ml
index c57b0185d..0e72cc8b0 100644
--- a/src/lib_shell_services/worker_services.ml
+++ b/src/lib_shell_services/worker_services.ml
@@ -69,16 +69,6 @@ module Peer_validators = struct
 
   module S = struct
 
-    let (peer_id_arg : P2p_peer.Id.t RPC_arg.t) =
-      RPC_arg.make
-        ~name:"peer_id"
-        ~descr:"The peer identifier of whom the prevalidator is responsible."
-        ~destruct:(fun s -> try
-                      Ok (P2p_peer.Id.of_b58check_exn s)
-                    with Failure msg -> Error msg)
-        ~construct:P2p_peer.Id.to_b58check
-        ()
-
     let list =
       RPC_service.get_service
         ~description:"Lists the peer validator workers and their status."
@@ -88,7 +78,7 @@ module Peer_validators = struct
              (obj2
                 (req "peer_id" P2p_peer.Id.encoding)
                 (req "status" (Worker_types.worker_status_encoding RPC_error.encoding))))
-        RPC_path.(root / "workers" / "peer_validators" /: Chain_services.chain_arg)
+        RPC_path.(root / "workers" / "chain_validators" /: Chain_services.chain_arg / "peers_validators" )
 
     let state =
       RPC_service.get_service
@@ -99,7 +89,7 @@ module Peer_validators = struct
              Peer_validator_worker_state.Request.encoding
              Peer_validator_worker_state.Event.encoding
              RPC_error.encoding)
-        RPC_path.(root / "workers" / "peer_validators" /: Chain_services.chain_arg /: peer_id_arg)
+        RPC_path.(root / "workers" / "chain_validators" /: Chain_services.chain_arg / "peers_validators" /: P2p_peer.Id.rpc_arg)
 
   end