feat: add meta to elicitation results (#792)

conformance/src/bin/client.rs

@@ -122,6 +122,7 @@ impl ClientHandler for ElicitationDefaultsClientHandler {
         Ok(CreateElicitationResult {
             action: ElicitationAction::Accept,
             content,
+            meta: None,
         })
     }
 }
@@ -174,6 +175,7 @@ impl ClientHandler for FullClientHandler {
         Ok(CreateElicitationResult {
             action: ElicitationAction::Accept,
             content: Some(json!({"username": "testuser", "email": "test@example.com"})),
+            meta: None,
         })
     }
 }

crates/rmcp/src/handler/client.rs

@@ -146,6 +146,7 @@ pub trait ClientHandler: Sized + Send + Sync + 'static {
     ///          Ok(CreateElicitationResult {
     ///             action: ElicitationAction::Accept,
     ///              content: Some(user_input),
+    ///              meta: None,
     ///          })
     ///         }
     ///         CreateElicitationRequestParam::UrlElicitationParam {meta, message, url, elicitation_id,} => {
@@ -154,6 +155,7 @@ pub trait ClientHandler: Sized + Send + Sync + 'static {
     ///          Ok(CreateElicitationResult {
     ///              action: ElicitationAction::Accept,
     ///             content: None,
+    ///             meta: None,
     ///             })
     ///         }
     ///     }
@@ -171,6 +173,7 @@ pub trait ClientHandler: Sized + Send + Sync + 'static {
         std::future::ready(Ok(CreateElicitationResult {
             action: ElicitationAction::Decline,
             content: None,
+            meta: None,
         }))
     }
 

crates/rmcp/src/model.rs

@@ -2699,6 +2699,10 @@ pub struct CreateElicitationResult {
     /// Only present when action is Accept.
     #[serde(skip_serializing_if = "Option::is_none")]
     pub content: Option<Value>,
+
+    /// Optional protocol-level metadata for this result.
+    #[serde(rename = "_meta", skip_serializing_if = "Option::is_none")]
+    pub meta: Option<Meta>,
 }
 
 impl CreateElicitationResult {
@@ -2707,6 +2711,7 @@ impl CreateElicitationResult {
         Self {
             action,
             content: None,
+            meta: None,
         }
     }
 
@@ -2715,6 +2720,12 @@ impl CreateElicitationResult {
         self.content = Some(content);
         self
     }
+
+    /// Set the metadata on this result.
+    pub fn with_meta(mut self, meta: Meta) -> Self {
+        self.meta = Some(meta);
+        self
+    }
 }
 
 /// Request type for creating an elicitation to gather user input

crates/rmcp/tests/test_elicitation.rs

@@ -1,6 +1,6 @@
 //cargo test --test test_elicitation --features "client server"
 
-use rmcp::{model::*, service::*};
+use rmcp::{model::*, object, service::*};
 // For typed elicitation tests
 #[cfg(feature = "schemars")]
 use schemars::JsonSchema;
@@ -98,6 +98,7 @@ async fn test_elicitation_result_serialization() {
     let accept_result = CreateElicitationResult {
         action: ElicitationAction::Accept,
         content: Some(json!({"email": "user@example.com"})),
+        meta: None,
     };
 
     let json = serde_json::to_value(&accept_result).unwrap();
@@ -111,6 +112,7 @@ async fn test_elicitation_result_serialization() {
     let decline_result = CreateElicitationResult {
         action: ElicitationAction::Decline,
         content: None,
+        meta: None,
     };
 
     let json = serde_json::to_value(&decline_result).unwrap();
@@ -124,6 +126,26 @@ async fn test_elicitation_result_serialization() {
     let deserialized: CreateElicitationResult = serde_json::from_value(expected).unwrap();
     assert_eq!(deserialized.action, ElicitationAction::Decline);
     assert_eq!(deserialized.content, None);
+    assert_eq!(deserialized.meta, None);
+
+    // Test protocol-level metadata round-trips as _meta.
+    let meta_result =
+        CreateElicitationResult::new(ElicitationAction::Accept).with_meta(Meta(object!({
+            "traceId": "elicitation-123"
+        })));
+
+    let json = serde_json::to_value(&meta_result).unwrap();
+    let expected = json!({
+        "action": "accept",
+        "_meta": {"traceId": "elicitation-123"}
+    });
+    assert_eq!(json, expected);
+
+    let deserialized: CreateElicitationResult = serde_json::from_value(expected).unwrap();
+    assert_eq!(
+        deserialized.meta,
+        Some(Meta(object!({ "traceId": "elicitation-123" })))
+    );
 }
 
 /// Test that elicitation requests can be created and handled through the JSON-RPC protocol
@@ -843,6 +865,7 @@ async fn test_elicitation_direction_server_to_client() {
     let client_result = ClientResult::CreateElicitationResult(CreateElicitationResult {
         action: ElicitationAction::Accept,
         content: Some(json!("John Doe")),
+        meta: None,
     });
 
     // Verify client result can be serialized
@@ -893,6 +916,7 @@ async fn test_elicitation_json_rpc_direction() {
         ClientResult::CreateElicitationResult(CreateElicitationResult {
             action: ElicitationAction::Accept,
             content: Some(json!(true)),
+            meta: None,
         }),
         RequestId::Number(1),
     );
@@ -928,6 +952,7 @@ async fn test_elicitation_actions_compliance() {
                 ElicitationAction::Accept => Some(serde_json::json!("some data")),
                 _ => None,
             },
+            meta: None,
         };
 
         let json = serde_json::to_value(&result).unwrap();
@@ -958,6 +983,7 @@ async fn test_elicitation_result_in_client_result() {
     let result = ClientResult::CreateElicitationResult(CreateElicitationResult {
         action: ElicitationAction::Decline,
         content: None,
+        meta: None,
     });
 
     match result {
@@ -2161,6 +2187,7 @@ async fn test_url_elicitation_action_workflow() {
     let accept_result = CreateElicitationResult {
         action: ElicitationAction::Accept,
         content: None, // URL elicitation doesn't return content, just confirmation
+        meta: None,
     };
 
     let json = serde_json::to_value(&accept_result).unwrap();
@@ -2172,6 +2199,7 @@ async fn test_url_elicitation_action_workflow() {
     let decline_result = CreateElicitationResult {
         action: ElicitationAction::Decline,
         content: None,
+        meta: None,
     };
 
     let json = serde_json::to_value(&decline_result).unwrap();
@@ -2181,6 +2209,7 @@ async fn test_url_elicitation_action_workflow() {
     let cancel_result = CreateElicitationResult {
         action: ElicitationAction::Cancel,
         content: None,
+        meta: None,
     };
 
     let json = serde_json::to_value(&cancel_result).unwrap();

crates/rmcp/tests/test_message_schema/client_json_rpc_message_schema.json

@@ -418,6 +418,14 @@
       "description": "The result returned by a client in response to an elicitation request.\n\nContains the user's decision (accept/decline/cancel) and optionally their input data\nif they chose to accept the request.",
       "type": "object",
       "properties": {
+        "_meta": {
+          "description": "Optional protocol-level metadata for this result.",
+          "type": [
+            "object",
+            "null"
+          ],
+          "additionalProperties": true
+        },
         "action": {
           "description": "The user's decision on how to handle the elicitation request",
           "allOf": [

crates/rmcp/tests/test_message_schema/client_json_rpc_message_schema_current.json

@@ -418,6 +418,14 @@
       "description": "The result returned by a client in response to an elicitation request.\n\nContains the user's decision (accept/decline/cancel) and optionally their input data\nif they chose to accept the request.",
       "type": "object",
       "properties": {
+        "_meta": {
+          "description": "Optional protocol-level metadata for this result.",
+          "type": [
+            "object",
+            "null"
+          ],
+          "additionalProperties": true
+        },
         "action": {
           "description": "The user's decision on how to handle the elicitation request",
           "allOf": [

crates/rmcp/tests/test_message_schema/server_json_rpc_message_schema.json

@@ -655,6 +655,14 @@
       "description": "The result returned by a client in response to an elicitation request.\n\nContains the user's decision (accept/decline/cancel) and optionally their input data\nif they chose to accept the request.",
       "type": "object",
       "properties": {
+        "_meta": {
+          "description": "Optional protocol-level metadata for this result.",
+          "type": [
+            "object",
+            "null"
+          ],
+          "additionalProperties": true
+        },
         "action": {
           "description": "The user's decision on how to handle the elicitation request",
           "allOf": [

crates/rmcp/tests/test_message_schema/server_json_rpc_message_schema_current.json

@@ -388,6 +388,7 @@
         "content": {
           "description": "The content returned by the tool (text, images, etc.)",
           "type": "array",
+          "default": [],
           "items": {
             "$ref": "#/definitions/Annotated"
           }
@@ -402,10 +403,7 @@
         "structuredContent": {
           "description": "An optional JSON object that represents the structured result of the tool call"
         }
-      },
+      }
-      "required": [
-        "content"
-      ]
     },
     "CancelTaskResult": {
       "description": "Response to a `tasks/cancel` request.\n\nPer spec, `CancelTaskResult = allOf[Result, Task]` — same shape as `GetTaskResult`.",
@@ -657,6 +655,14 @@
       "description": "The result returned by a client in response to an elicitation request.\n\nContains the user's decision (accept/decline/cancel) and optionally their input data\nif they chose to accept the request.",
       "type": "object",
       "properties": {
+        "_meta": {
+          "description": "Optional protocol-level metadata for this result.",
+          "type": [
+            "object",
+            "null"
+          ],
+          "additionalProperties": true
+        },
         "action": {
           "description": "The user's decision on how to handle the elicitation request",
           "allOf": [