Pass requestId to handlers via metadata

src/server/mcp.test.ts

@@ -101,6 +101,7 @@ describe("ResourceTemplate", () => {
     const abortController = new AbortController();
     const result = await template.listCallback?.({
       signal: abortController.signal,
+      requestId: 'not-implemented',
       sendRequest: () => { throw new Error("Not implemented") },
       sendNotification: () => { throw new Error("Not implemented") }
     });
@@ -646,6 +647,59 @@ describe("tool()", () => {
     expect(receivedSessionId).toBe("test-session-123");
   });
 
+  test("should pass requestId to tool callback via RequestHandlerExtra", async () => {
+    const mcpServer = new McpServer({
+      name: "test server",
+      version: "1.0",
+    });
+
+    const client = new Client(
+      {
+        name: "test client",
+        version: "1.0",
+      },
+      {
+        capabilities: {
+          tools: {},
+        },
+      },
+    );
+
+    let receivedRequestId: string | number | undefined;
+    mcpServer.tool("request-id-test", async (extra) => {
+      receivedRequestId = extra.requestId;
+      return {
+        content: [
+          {
+            type: "text",
+            text: `Received request ID: ${extra.requestId}`,
+          },
+        ],
+      };
+    });
+
+    const [clientTransport, serverTransport] = InMemoryTransport.createLinkedPair();
+
+    await Promise.all([
+      client.connect(clientTransport),
+      mcpServer.server.connect(serverTransport),
+    ]);
+
+    const result = await client.request(
+      {
+        method: "tools/call",
+        params: {
+          name: "request-id-test",
+        },
+      },
+      CallToolResultSchema,
+    );
+
+    expect(receivedRequestId).toBeDefined();
+    expect(typeof receivedRequestId === 'string' || typeof receivedRequestId === 'number').toBe(true);
+    expect(result.content[0].text).toContain("Received request ID:");
+  });
+
   test("should provide sendNotification within tool call", async () => {
     const mcpServer = new McpServer(
       {
@@ -1702,6 +1756,59 @@ describe("resource()", () => {
     expect(result.completion.values).toEqual(["movies", "music"]);
     expect(result.completion.total).toBe(2);
   });
+
+  test("should pass requestId to resource callback via RequestHandlerExtra", async () => {
+    const mcpServer = new McpServer({
+      name: "test server",
+      version: "1.0",
+    });
+
+    const client = new Client(
+      {
+        name: "test client",
+        version: "1.0",
+      },
+      {
+        capabilities: {
+          resources: {},
+        },
+      },
+    );
+
+    let receivedRequestId: string | number | undefined;
+    mcpServer.resource("request-id-test", "test://resource", async (_uri, extra) => {
+      receivedRequestId = extra.requestId;
+      return {
+        contents: [
+          {
+            uri: "test://resource",
+            text: `Received request ID: ${extra.requestId}`,
+          },
+        ],
+      };
+    });
+
+    const [clientTransport, serverTransport] = InMemoryTransport.createLinkedPair();
+
+    await Promise.all([
+      client.connect(clientTransport),
+      mcpServer.server.connect(serverTransport),
+    ]);
+
+    const result = await client.request(
+      {
+        method: "resources/read",
+        params: {
+          uri: "test://resource",
+        },
+      },
+      ReadResourceResultSchema,
+    );
+
+    expect(receivedRequestId).toBeDefined();
+    expect(typeof receivedRequestId === 'string' || typeof receivedRequestId === 'number').toBe(true);
+    expect(result.contents[0].text).toContain("Received request ID:");
+  });
 });
 
 describe("prompt()", () => {
@@ -2511,4 +2618,60 @@ describe("prompt()", () => {
     expect(result.completion.values).toEqual(["Alice"]);
     expect(result.completion.total).toBe(1);
   });
+
+  test("should pass requestId to prompt callback via RequestHandlerExtra", async () => {
+    const mcpServer = new McpServer({
+      name: "test server",
+      version: "1.0",
+    });
+
+    const client = new Client(
+      {
+        name: "test client",
+        version: "1.0",
+      },
+      {
+        capabilities: {
+          prompts: {},
+        },
+      },
+    );
+
+    let receivedRequestId: string | number | undefined;
+    mcpServer.prompt("request-id-test", async (extra) => {
+      receivedRequestId = extra.requestId;
+      return {
+        messages: [
+          {
+            role: "assistant",
+            content: {
+              type: "text",
+              text: `Received request ID: ${extra.requestId}`,
+            },
+          },
+        ],
+      };
+    });
+
+    const [clientTransport, serverTransport] = InMemoryTransport.createLinkedPair();
+
+    await Promise.all([
+      client.connect(clientTransport),
+      mcpServer.server.connect(serverTransport),
+    ]);
+
+    const result = await client.request(
+      {
+        method: "prompts/get",
+        params: {
+          name: "request-id-test",
+        },
+      },
+      GetPromptResultSchema,
+    );
+
+    expect(receivedRequestId).toBeDefined();
+    expect(typeof receivedRequestId === 'string' || typeof receivedRequestId === 'number').toBe(true);
+    expect(result.messages[0].content.text).toContain("Received request ID:");
+  });
 });

src/shared/protocol.ts

@@ -115,6 +115,12 @@ export type RequestHandlerExtra<SendRequestT extends Request,
      */
     sessionId?: string;
 
+    /**
+     * The JSON-RPC ID of the request being handled.
+     * This can be useful for tracking or logging purposes.
+     */
+    requestId: RequestId;
+
     /**
      * Sends a notification that relates to the current request being handled.
      * 
@@ -361,6 +367,7 @@ export abstract class Protocol<
       sendRequest: (r, resultSchema, options?) =>
         this.request(r, resultSchema, { ...options, relatedRequestId: request.id }),
       authInfo: extra?.authInfo,
+      requestId: request.id,
     };
 
     // Starting with Promise.resolve() puts any synchronous errors into the monad as well.