Meta support extensions

Author: =

crates/rmcp/src/model.rs

@@ -191,12 +191,24 @@ impl<'de> Deserialize<'de> for NumberOrString {
 }
 
 pub type RequestId = NumberOrString;
-pub type ProgressToken = NumberOrString;
 
 #[derive(Debug, Serialize, Deserialize, Clone, PartialEq)]
+#[serde(transparent)]
+pub struct ProgressToken(pub NumberOrString);
+
+
+#[derive(Debug, Serialize, Deserialize, Clone, PartialEq, Default)]
 #[serde(rename_all = "camelCase")]
 pub struct RequestMeta {
-    pub progress_token: ProgressToken,
+    pub progress_token: Option<ProgressToken>,
+    #[serde(flatten)]
+    pub ext: JsonObject
+}
+
+impl RequestMeta {
+    pub fn is_empty(&self) -> bool {
+        self.progress_token.is_none() && self.ext.is_empty()
+    }
 }
 
 #[derive(Debug, Serialize, Deserialize, Clone, PartialEq)]
@@ -841,8 +853,8 @@ const_string!(CallToolRequestMethod = "tools/call");
 #[derive(Debug, Serialize, Deserialize, Clone, PartialEq)]
 #[serde(rename_all = "camelCase")]
 pub struct CallToolRequestParam {
-    #[serde(skip_serializing_if = "Option::is_none")]
-    pub _meta: Option<RequestMeta>,
+    #[serde(skip_serializing_if = "RequestMeta::is_empty", default)]
+    pub _meta: RequestMeta,
     pub name: Cow<'static, str>,
     #[serde(skip_serializing_if = "Option::is_none")]
     pub arguments: Option<JsonObject>,

crates/rmcp/src/model/meta.rs

@@ -1,34 +1,34 @@
 use super::{ClientRequest, RequestMeta, ServerRequest};
 
 pub trait WithMeta<M> {
-    fn set_meta(&mut self, meta: Option<M>);
+    fn get_meta_mut(&mut self) -> Option<&mut M>;
     fn get_meta(&self) -> Option<&M>;
 }
 
 impl WithMeta<RequestMeta> for ClientRequest {
-    fn set_meta(&mut self, meta: Option<RequestMeta>) {
+    fn get_meta_mut(&mut self) -> Option<&mut RequestMeta> {
         #[allow(clippy::single_match)]
         match self {
-            ClientRequest::CallToolRequest(req) => {
-                req.params._meta = meta;
-            }
-            _ => {}
+            ClientRequest::CallToolRequest(req) => Some(&mut req.params._meta),
+            _ => None,
         }
     }
 
     fn get_meta(&self) -> Option<&RequestMeta> {
         #[allow(clippy::single_match)]
         match self {
-            ClientRequest::CallToolRequest(req) => req.params._meta.as_ref(),
+            ClientRequest::CallToolRequest(req) => Some(&req.params._meta),
             _ => None,
         }
     }
 }
 
 impl WithMeta<RequestMeta> for ServerRequest {
-    fn set_meta(&mut self, _meta: Option<RequestMeta>) {}
-
     fn get_meta(&self) -> Option<&RequestMeta> {
         None
     }
+
+    fn get_meta_mut(&mut self) -> Option<&mut RequestMeta> {
+        None
+    }
 }

crates/rmcp/src/service.rs

@@ -6,7 +6,8 @@ use crate::{
     model::{
         CancelledNotification, CancelledNotificationParam, JsonRpcBatchRequestItem,
         JsonRpcBatchResponseItem, JsonRpcError, JsonRpcMessage, JsonRpcNotification,
-        JsonRpcRequest, JsonRpcResponse, ProgressToken, RequestId, RequestMeta, WithMeta,
+        JsonRpcRequest, JsonRpcResponse, NumberOrString, ProgressToken, RequestId, RequestMeta,
+        WithMeta,
     },
     transport::IntoTransport,
 };
@@ -220,8 +221,10 @@ impl RequestIdProvider for AtomicU32Provider {
 }
 
 impl ProgressTokenProvider for AtomicU32Provider {
-    fn next_progress_token(&self) -> RequestId {
-        RequestId::Number(self.id.fetch_add(1, std::sync::atomic::Ordering::SeqCst))
+    fn next_progress_token(&self) -> ProgressToken {
+        ProgressToken(NumberOrString::Number(
+            self.id.fetch_add(1, std::sync::atomic::Ordering::SeqCst),
+        ))
     }
 }
 
@@ -379,9 +382,9 @@ impl<R: ServiceRole> Peer<R> {
     ) -> Result<RequestHandle<R>, ServiceError> {
         let id = self.request_id_provider.next_request_id();
         let progress_token = self.progress_token_provider.next_progress_token();
-        request.set_meta(Some(RequestMeta {
-            progress_token: progress_token.clone(),
-        }));
+        if let Some(meta) = request.get_meta_mut() {
+            meta.progress_token = Some(progress_token.clone());
+        };
         let (responder, receiver) = tokio::sync::oneshot::channel();
         self.tx
             .send(PeerSinkMessage::Request {

crates/rmcp/src/transport/streamable_http/session.rs

@@ -61,7 +61,7 @@ impl Session {
         if self.request_router.contains_key(&request_id) {
             return Err(SessionError::DuplicatedRequestId(request_id.clone()));
         };
-        let progress_token = request.get_meta().map(|meta| meta.progress_token.clone());
+        let progress_token = request.get_meta().and_then(|meta| meta.progress_token.clone());
         let (tx, rx) = tokio::sync::mpsc::channel(Self::REQUEST_WISE_CHANNEL_SIZE);
         self.send_to_service(ClientJsonRpcMessage::Request(JsonRpcRequest {
             request,

examples/clients/src/collection.rs

@@ -39,6 +39,7 @@ async fn main() -> Result<()> {
             .call_tool(CallToolRequestParam {
                 name: "git_status".into(),
                 arguments: serde_json::json!({ "repo_path": "." }).as_object().cloned(),
+                _meta: Default::default(),
             })
             .await?;
     }

examples/clients/src/everything_stdio.rs

@@ -41,6 +41,7 @@ async fn main() -> Result<()> {
         .call_tool(CallToolRequestParam {
             name: "echo".into(),
             arguments: Some(object!({ "message": "hi from rmcp" })),
+            _meta: Default::default(),
         })
         .await?;
     tracing::info!("Tool result for echo: {tool_result:#?}");
@@ -50,6 +51,7 @@ async fn main() -> Result<()> {
         .call_tool(CallToolRequestParam {
             name: "longRunningOperation".into(),
             arguments: Some(object!({ "duration": 3, "steps": 1 })),
+            _meta: Default::default(),
         })
         .await?;
     tracing::info!("Tool result for longRunningOperation: {tool_result:#?}");

examples/clients/src/sse.rs

@@ -41,6 +41,7 @@ async fn main() -> Result<()> {
         .call_tool(CallToolRequestParam {
             name: "increment".into(),
             arguments: serde_json::json!({}).as_object().cloned(),
+            _meta: Default::default(),
         })
         .await?;
     tracing::info!("Tool result: {tool_result:#?}");

examples/clients/src/std_io.rs

@@ -39,6 +39,7 @@ async fn main() -> Result<()> {
         .call_tool(CallToolRequestParam {
             name: "git_status".into(),
             arguments: serde_json::json!({ "repo_path": "." }).as_object().cloned(),
+            _meta: Default::default(),
         })
         .await?;
     tracing::info!("Tool result: {tool_result:#?}");

examples/rig-integration/src/mcp_adaptor.rs

@@ -42,6 +42,7 @@ impl RigTool for McpToolAdaptor {
                     name: self.tool.name.clone(),
                     arguments: serde_json::from_str(&args)
                         .map_err(rig::tool::ToolError::JsonError)?,
+                    _meta: Default::default(),
                 })
                 .await
                 .map_err(|e| rig::tool::ToolError::ToolCallError(Box::new(e)))?;

examples/transport/src/unix_socket.rs

@@ -72,6 +72,7 @@ async fn client() -> anyhow::Result<()> {
                     "a": 10,
                     "b": 20
                 })),
+                _meta: Default::default()
             })
             .await?;