diff --git a/src/minutils/RPC.ml b/src/minutils/RPC.ml
index 95a1b861e..ea58839e2 100644
--- a/src/minutils/RPC.ml
+++ b/src/minutils/RPC.ml
@@ -98,7 +98,15 @@ module Description = struct
 
 end
 
-module Answer = RestoDirectory.Answer
+module Answer = struct
+
+  include RestoDirectory.Answer
+
+  let answer ?(code = 200) json = { code; body = Single json }
+  let return ?code json = Lwt.return (answer ?code json)
+
+end
+
 
 type step =
   | Static of string
diff --git a/src/minutils/RPC.mli b/src/minutils/RPC.mli
index d5a2e57e0..2a7344311 100644
--- a/src/minutils/RPC.mli
+++ b/src/minutils/RPC.mli
@@ -184,7 +184,8 @@ module Answer : sig
   }
 
   val ok: 'a -> 'a answer
-  val return: 'a -> 'a answer Lwt.t
+  val answer: ?code:int -> 'a -> 'a answer
+  val return: ?code:int -> 'a -> 'a answer Lwt.t
   val return_stream: 'a stream -> 'a answer Lwt.t
 
 end
diff --git a/src/minutils/data_encoding.ml b/src/minutils/data_encoding.ml
index 1507196b9..17cb3f981 100644
--- a/src/minutils/data_encoding.ml
+++ b/src/minutils/data_encoding.ml
@@ -698,6 +698,17 @@ module Encoding = struct
         `Variable in
     make @@ Mu (kind, name, self)
 
+  let result ok_enc error_enc =
+    union
+      ~tag_size:`Uint8
+      [ case ~tag:1 ok_enc
+          (function Ok x -> Some x | Error _ -> None)
+          (fun x -> Ok x) ;
+        case ~tag:0 error_enc
+          (function Ok _ -> None | Error x -> Some x)
+          (fun x -> Error x) ;
+      ]
+
   let assoc enc =
     let json = Json_encoding.assoc (Json.get_json enc) in
     let binary = list (tup2 string enc) in
diff --git a/src/minutils/data_encoding.mli b/src/minutils/data_encoding.mli
index 98adf1588..5066d3be4 100644
--- a/src/minutils/data_encoding.mli
+++ b/src/minutils/data_encoding.mli
@@ -47,6 +47,7 @@ val string : string encoding
 val bytes : MBytes.t encoding
 val float : float encoding
 val option : 'a encoding -> 'a option encoding
+val result : 'a encoding -> 'b encoding -> ('a, 'b) result encoding
 val string_enum : (string * 'a) list -> 'a encoding
 
 module Fixed : sig
diff --git a/src/proto/environment/RPC.mli b/src/proto/environment/RPC.mli
index bbefb2eee..8c1ee6346 100644
--- a/src/proto/environment/RPC.mli
+++ b/src/proto/environment/RPC.mli
@@ -98,7 +98,8 @@ module Answer : sig
   }
 
   val ok: 'a -> 'a answer
-  val return: 'a -> 'a answer Lwt.t
+  val answer: ?code:int -> 'a -> 'a answer
+  val return: ?code:int -> 'a -> 'a answer Lwt.t
 
 end