Implementation of SEP-986: Specify Format for Tool Names (#900)

Co-authored-by: Felix Weinberger <fweinberger@anthropic.com>
Co-authored-by: Felix Weinberger <3823880+felixweinberger@users.noreply.github.com>

src/server/mcp.test.ts

@@ -227,6 +227,10 @@ describe('ResourceTemplate', () => {
 });
 
 describe('tool()', () => {
+    afterEach(() => {
+        jest.restoreAllMocks();
+    });
+
     /***
      * Test: Zero-Argument Tool Registration
      */
@@ -1692,6 +1696,56 @@ describe('tool()', () => {
         expect(result.tools[0].name).toBe('test-without-meta');
         expect(result.tools[0]._meta).toBeUndefined();
     });
+
+    test('should validate tool names according to SEP specification', () => {
+        // Create a new server instance for this test
+        const testServer = new McpServer({
+            name: 'test server',
+            version: '1.0'
+        });
+
+        // Spy on console.warn to verify warnings are logged
+        const warnSpy = jest.spyOn(console, 'warn').mockImplementation();
+
+        // Test valid tool names
+        testServer.registerTool(
+            'valid-tool-name',
+            {
+                description: 'A valid tool name'
+            },
+            async () => ({ content: [{ type: 'text' as const, text: 'Success' }] })
+        );
+
+        // Test tool name with warnings (starts with dash)
+        testServer.registerTool(
+            '-warning-tool',
+            {
+                description: 'A tool name that generates warnings'
+            },
+            async () => ({ content: [{ type: 'text' as const, text: 'Success' }] })
+        );
+
+        // Test invalid tool name (contains spaces)
+        testServer.registerTool(
+            'invalid tool name',
+            {
+                description: 'An invalid tool name'
+            },
+            async () => ({ content: [{ type: 'text' as const, text: 'Success' }] })
+        );
+
+        // Verify that warnings were issued (both for warnings and validation failures)
+        expect(warnSpy).toHaveBeenCalled();
+
+        // Verify specific warning content
+        const warningCalls = warnSpy.mock.calls.map(call => call.join(' '));
+        expect(warningCalls.some(call => call.includes('Tool name starts or ends with a dash'))).toBe(true);
+        expect(warningCalls.some(call => call.includes('Tool name contains spaces'))).toBe(true);
+        expect(warningCalls.some(call => call.includes('Tool name contains invalid characters'))).toBe(true);
+
+        // Clean up spies
+        warnSpy.mockRestore();
+    });
 });
 
 describe('resource()', () => {

src/server/mcp.ts

@@ -40,6 +40,7 @@ import { Completable, CompletableDef } from './completable.js';
 import { UriTemplate, Variables } from '../shared/uriTemplate.js';
 import { RequestHandlerExtra } from '../shared/protocol.js';
 import { Transport } from '../shared/transport.js';
+import { validateAndWarnToolName } from '../shared/toolNameValidation.js';
 
 /**
  * High-level MCP server that provides a simpler API for working with resources, tools, and prompts.
@@ -664,6 +665,9 @@ export class McpServer {
         _meta: Record<string, unknown> | undefined,
         callback: ToolCallback<ZodRawShape | undefined>
     ): RegisteredTool {
+        // Validate tool name according to SEP specification
+        validateAndWarnToolName(name);
+
         const registeredTool: RegisteredTool = {
             title,
             description,
@@ -678,6 +682,9 @@ export class McpServer {
             remove: () => registeredTool.update({ name: null }),
             update: updates => {
                 if (typeof updates.name !== 'undefined' && updates.name !== name) {
+                    if (typeof updates.name === 'string') {
+                        validateAndWarnToolName(updates.name);
+                    }
                     delete this._registeredTools[name];
                     if (updates.name) this._registeredTools[updates.name] = registeredTool;
                 }