Fix: Respect explicit listChanged: false capability setting (#1513)

Author: mattzcarey

packages/server/src/server/mcp.ts

@@ -117,7 +117,7 @@ export class McpServer {
 
         this.server.registerCapabilities({
             tools: {
-                listChanged: true
+                listChanged: this.server.getCapabilities().tools?.listChanged ?? true
             }
         });
 
@@ -429,7 +429,7 @@ export class McpServer {
 
         this.server.registerCapabilities({
             resources: {
-                listChanged: true
+                listChanged: this.server.getCapabilities().resources?.listChanged ?? true
             }
         });
 
@@ -509,7 +509,7 @@ export class McpServer {
 
         this.server.registerCapabilities({
             prompts: {
-                listChanged: true
+                listChanged: this.server.getCapabilities().prompts?.listChanged ?? true
             }
         });
 

packages/server/src/server/server.ts

@@ -452,7 +452,10 @@ export class Server extends Protocol<ServerContext> {
         return this._clientVersion;
     }
 
-    private getCapabilities(): ServerCapabilities {
+    /**
+     * Returns the current server capabilities.
+     */
+    public getCapabilities(): ServerCapabilities {
         return this._capabilities;
     }
 

test/integration/test/server/mcp.test.ts

@@ -782,6 +782,96 @@ describe('Zod v4', () => {
             ]);
         });
 
+        /***
+         * Test: listChanged capability should default to true when not specified
+         */
+        test('should default tools.listChanged to true when not explicitly set', async () => {
+            const mcpServer = new McpServer({
+                name: 'test server',
+                version: '1.0'
+            });
+            const client = new Client({
+                name: 'test client',
+                version: '1.0'
+            });
+
+            mcpServer.registerTool('test', {}, async () => ({
+                content: [{ type: 'text', text: 'Test' }]
+            }));
+
+            const [clientTransport, serverTransport] = InMemoryTransport.createLinkedPair();
+            await Promise.all([client.connect(clientTransport), mcpServer.connect(serverTransport)]);
+
+            const capabilities = client.getServerCapabilities();
+            expect(capabilities?.tools?.listChanged).toBe(true);
+        });
+
+        /***
+         * Test: listChanged capability should respect explicit false setting
+         */
+        test('should respect tools.listChanged: false when explicitly set', async () => {
+            const mcpServer = new McpServer({ name: 'test server', version: '1.0' }, { capabilities: { tools: { listChanged: false } } });
+            const client = new Client({
+                name: 'test client',
+                version: '1.0'
+            });
+
+            mcpServer.registerTool('test', {}, async () => ({
+                content: [{ type: 'text', text: 'Test' }]
+            }));
+
+            const [clientTransport, serverTransport] = InMemoryTransport.createLinkedPair();
+            await Promise.all([client.connect(clientTransport), mcpServer.connect(serverTransport)]);
+
+            const capabilities = client.getServerCapabilities();
+            expect(capabilities?.tools?.listChanged).toBe(false);
+        });
+
+        /***
+         * Test: resources.listChanged should respect explicit false setting
+         */
+        test('should respect resources.listChanged: false when explicitly set', async () => {
+            const mcpServer = new McpServer(
+                { name: 'test server', version: '1.0' },
+                { capabilities: { resources: { listChanged: false } } }
+            );
+            const client = new Client({
+                name: 'test client',
+                version: '1.0'
+            });
+
+            mcpServer.registerResource('test://resource', 'Test Resource', async () => ({
+                contents: [{ uri: 'test://resource', text: 'Test' }]
+            }));
+
+            const [clientTransport, serverTransport] = InMemoryTransport.createLinkedPair();
+            await Promise.all([client.connect(clientTransport), mcpServer.connect(serverTransport)]);
+
+            const capabilities = client.getServerCapabilities();
+            expect(capabilities?.resources?.listChanged).toBe(false);
+        });
+
+        /***
+         * Test: prompts.listChanged should respect explicit false setting
+         */
+        test('should respect prompts.listChanged: false when explicitly set', async () => {
+            const mcpServer = new McpServer({ name: 'test server', version: '1.0' }, { capabilities: { prompts: { listChanged: false } } });
+            const client = new Client({
+                name: 'test client',
+                version: '1.0'
+            });
+
+            mcpServer.registerPrompt('test-prompt', async () => ({
+                messages: [{ role: 'assistant', content: { type: 'text', text: 'Test' } }]
+            }));
+
+            const [clientTransport, serverTransport] = InMemoryTransport.createLinkedPair();
+            await Promise.all([client.connect(clientTransport), mcpServer.connect(serverTransport)]);
+
+            const capabilities = client.getServerCapabilities();
+            expect(capabilities?.prompts?.listChanged).toBe(false);
+        });
+
         /***
          * Test: Tool Registration with Parameters
          */