feat(mcp): add option to infer mcp client

Author: stainless-app[bot]

packages/mcp-server/src/compat.ts

@@ -20,13 +20,13 @@ export const defaultClientCapabilities: ClientCapabilities = {
   toolNameLength: undefined,
 };
 
-export const ClientType = z.enum(['openai-agents', 'claude', 'claude-code', 'cursor']);
+export const ClientType = z.enum(['openai-agents', 'claude', 'claude-code', 'cursor', 'infer']);
 export type ClientType = z.infer<typeof ClientType>;
 
 // Client presets for compatibility
 // Note that these could change over time as models get better, so this is
 // a best effort.
-export const knownClients: Record<ClientType, ClientCapabilities> = {
+export const knownClients: Record<Exclude<ClientType, 'infer'>, ClientCapabilities> = {
   'openai-agents': {
     topLevelUnions: false,
     validJson: true,

packages/mcp-server/src/http.ts

@@ -8,7 +8,6 @@ import { fromError } from 'zod-validation-error/v3';
 import { McpOptions, parseQueryOptions } from './options';
 import { initMcpServer, newMcpServer } from './server';
 import { parseAuthHeaders } from './headers';
-import { Endpoint } from './tools';
 
 const newServer = (
   defaultMcpOptions: McpOptions,
@@ -101,11 +100,7 @@ export const streamableHTTPApp = (options: McpOptions): express.Express => {
   return app;
 };
 
-export const launchStreamableHTTPServer = async (
-  options: McpOptions,
-  endpoints: Endpoint[],
-  port: number | string | undefined,
-) => {
+export const launchStreamableHTTPServer = async (options: McpOptions, port: number | string | undefined) => {
   const app = streamableHTTPApp(options);
   const server = app.listen(port);
   const address = server.address();

packages/mcp-server/src/index.ts

@@ -23,10 +23,10 @@ async function main() {
 
   switch (options.transport) {
     case 'stdio':
-      await launchStdioServer(options, selectedTools);
+      await launchStdioServer(options);
       break;
     case 'http':
-      await launchStreamableHTTPServer(options, selectedTools, options.port ?? options.socket);
+      await launchStreamableHTTPServer(options, options.port ?? options.socket);
       break;
   }
 }

packages/mcp-server/src/options.ts

@@ -13,12 +13,12 @@ export type CLIOptions = McpOptions & {
 };
 
 export type McpOptions = {
-  client: ClientType | undefined;
-  includeDynamicTools: boolean | undefined;
-  includeAllTools: boolean | undefined;
-  includeCodeTools: boolean | undefined;
-  filters: Filter[];
-  capabilities?: Partial<ClientCapabilities>;
+  client?: ClientType | undefined;
+  includeDynamicTools?: boolean | undefined;
+  includeAllTools?: boolean | undefined;
+  includeCodeTools?: boolean | undefined;
+  filters?: Filter[] | undefined;
+  capabilities?: Partial<ClientCapabilities> | undefined;
 };
 
 const CAPABILITY_CHOICES = [
@@ -204,14 +204,7 @@ export function parseCLIOptions(): CLIOptions {
   }
 
   // Parse client capabilities
-  const clientCapabilities: ClientCapabilities = {
-    topLevelUnions: true,
-    validJson: true,
-    refs: true,
-    unions: true,
-    formats: true,
-    toolNameLength: undefined,
-  };
+  const clientCapabilities: Partial<ClientCapabilities> = {};
 
   // Apply individual capability overrides
   if (Array.isArray(argv.capability)) {
@@ -264,7 +257,7 @@ export function parseCLIOptions(): CLIOptions {
 
   const client = argv.client as ClientType;
   return {
-    client: client && knownClients[client] ? client : undefined,
+    client: client && client !== 'infer' && knownClients[client] ? client : undefined,
     includeDynamicTools,
     includeAllTools,
     includeCodeTools,
@@ -310,7 +303,7 @@ export function parseQueryOptions(defaultOptions: McpOptions, query: unknown): M
   const queryObject = typeof query === 'string' ? qs.parse(query) : query;
   const queryOptions = QueryOptions.parse(queryObject);
 
-  const filters: Filter[] = [...defaultOptions.filters];
+  const filters: Filter[] = [...(defaultOptions.filters ?? [])];
 
   for (const resource of queryOptions.resource || []) {
     filters.push({ type: 'resource', op: 'include', value: resource });
@@ -338,15 +331,7 @@ export function parseQueryOptions(defaultOptions: McpOptions, query: unknown): M
   }
 
   // Parse client capabilities
-  const clientCapabilities: ClientCapabilities = {
-    topLevelUnions: true,
-    validJson: true,
-    refs: true,
-    unions: true,
-    formats: true,
-    toolNameLength: undefined,
-    ...defaultOptions.capabilities,
-  };
+  const clientCapabilities: Partial<ClientCapabilities> = { ...defaultOptions.capabilities };
 
   for (const cap of queryOptions.capability || []) {
     const parsed = parseCapabilityValue(cap);
@@ -384,12 +369,13 @@ export function parseQueryOptions(defaultOptions: McpOptions, query: unknown): M
   return {
     client: queryOptions.client ?? defaultOptions.client,
     includeDynamicTools:
-      defaultOptions.includeDynamicTools ??
-      (queryOptions.tools?.includes('dynamic') && !queryOptions.no_tools?.includes('dynamic')),
+      defaultOptions.includeDynamicTools === false ?
+        false
+      : queryOptions.tools?.includes('dynamic') && !queryOptions.no_tools?.includes('dynamic'),
     includeAllTools:
-      defaultOptions.includeAllTools ??
-      (queryOptions.tools?.includes('all') && !queryOptions.no_tools?.includes('all')),
-    // Never include code tools on remote server.
+      defaultOptions.includeAllTools === false ?
+        false
+      : queryOptions.tools?.includes('all') && !queryOptions.no_tools?.includes('all'),
     includeCodeTools: undefined,
     filters,
     capabilities: clientCapabilities,

packages/mcp-server/src/server.ts

@@ -3,7 +3,12 @@
 import { Server } from '@modelcontextprotocol/sdk/server/index.js';
 import { McpServer } from '@modelcontextprotocol/sdk/server/mcp.js';
 import { Endpoint, endpoints, HandlerFunction, query } from './tools';
-import { CallToolRequestSchema, ListToolsRequestSchema, Tool } from '@modelcontextprotocol/sdk/types.js';
+import {
+  CallToolRequestSchema,
+  Implementation,
+  ListToolsRequestSchema,
+  Tool,
+} from '@modelcontextprotocol/sdk/types.js';
 import { ClientOptions } from '@flowglad/node';
 import Flowglad from '@flowglad/node';
 import {
@@ -41,29 +46,29 @@ export const server = newMcpServer();
  */
 export function initMcpServer(params: {
   server: Server | McpServer;
-  clientOptions: ClientOptions;
-  mcpOptions: McpOptions;
-  endpoints?: { tool: Tool; handler: HandlerFunction }[];
-}) {
-  const transformedEndpoints = selectTools(endpoints, params.mcpOptions);
-  const client = new Flowglad(params.clientOptions);
-  const capabilities = {
-    ...defaultClientCapabilities,
-    ...(params.mcpOptions.client ? knownClients[params.mcpOptions.client] : params.mcpOptions.capabilities),
-  };
-  init({ server: params.server, client, endpoints: transformedEndpoints, capabilities });
-}
-
-export function init(params: {
-  server: Server | McpServer;
-  client?: Flowglad;
-  endpoints?: { tool: Tool; handler: HandlerFunction }[];
-  capabilities?: Partial<ClientCapabilities>;
+  clientOptions?: ClientOptions;
+  mcpOptions?: McpOptions;
 }) {
   const server = params.server instanceof McpServer ? params.server.server : params.server;
-  const providedEndpoints = params.endpoints || endpoints;
-
-  const endpointMap = Object.fromEntries(providedEndpoints.map((endpoint) => [endpoint.tool.name, endpoint]));
+  const mcpOptions = params.mcpOptions ?? {};
+
+  let providedEndpoints: Endpoint[] | null = null;
+  let endpointMap: Record<string, Endpoint> | null = null;
+
+  const initTools = (implementation?: Implementation) => {
+    if (implementation && (!mcpOptions.client || mcpOptions.client === 'infer')) {
+      mcpOptions.client =
+        implementation.name.toLowerCase().includes('claude') ? 'claude'
+        : implementation.name.toLowerCase().includes('cursor') ? 'cursor'
+        : undefined;
+      mcpOptions.capabilities = {
+        ...(mcpOptions.client && knownClients[mcpOptions.client]),
+        ...mcpOptions.capabilities,
+      };
+    }
+    providedEndpoints = selectTools(endpoints, mcpOptions);
+    endpointMap = Object.fromEntries(providedEndpoints.map((endpoint) => [endpoint.tool.name, endpoint]));
+  };
 
   const logAtLevel =
     (level: 'debug' | 'info' | 'warning' | 'error') =>
@@ -80,51 +85,63 @@ export function init(params: {
     error: logAtLevel('error'),
   };
 
-  const client =
-    params.client || new Flowglad({ defaultHeaders: { 'X-Stainless-MCP': 'true' }, logger: logger });
+  const client = new Flowglad({
+    logger,
+    ...params.clientOptions,
+    defaultHeaders: {
+      ...params.clientOptions?.defaultHeaders,
+      'X-Stainless-MCP': 'true',
+    },
+  });
 
   server.setRequestHandler(ListToolsRequestSchema, async () => {
+    if (providedEndpoints === null) {
+      initTools(server.getClientVersion());
+    }
     return {
-      tools: providedEndpoints.map((endpoint) => endpoint.tool),
+      tools: providedEndpoints!.map((endpoint) => endpoint.tool),
     };
   });
 
   server.setRequestHandler(CallToolRequestSchema, async (request) => {
+    if (endpointMap === null) {
+      initTools(server.getClientVersion());
+    }
     const { name, arguments: args } = request.params;
-    const endpoint = endpointMap[name];
+    const endpoint = endpointMap![name];
     if (!endpoint) {
       throw new Error(`Unknown tool: ${name}`);
     }
 
-    return executeHandler(endpoint.tool, endpoint.handler, client, args, params.capabilities);
+    return executeHandler(endpoint.tool, endpoint.handler, client, args, mcpOptions.capabilities);
   });
 }
 
 /**
  * Selects the tools to include in the MCP Server based on the provided options.
  */
-export function selectTools(endpoints: Endpoint[], options: McpOptions): Endpoint[] {
-  const filteredEndpoints = query(options.filters, endpoints);
+export function selectTools(endpoints: Endpoint[], options?: McpOptions): Endpoint[] {
+  const filteredEndpoints = query(options?.filters ?? [], endpoints);
 
   let includedTools = filteredEndpoints;
 
   if (includedTools.length > 0) {
-    if (options.includeDynamicTools) {
+    if (options?.includeDynamicTools) {
       includedTools = dynamicTools(includedTools);
     }
   } else {
-    if (options.includeAllTools) {
+    if (options?.includeAllTools) {
       includedTools = endpoints;
-    } else if (options.includeDynamicTools) {
+    } else if (options?.includeDynamicTools) {
       includedTools = dynamicTools(endpoints);
-    } else if (options.includeCodeTools) {
+    } else if (options?.includeCodeTools) {
       includedTools = [codeTool()];
     } else {
       includedTools = endpoints;
     }
   }
 
-  const capabilities = { ...defaultClientCapabilities, ...options.capabilities };
+  const capabilities = { ...defaultClientCapabilities, ...options?.capabilities };
   return applyCompatibilityTransformations(includedTools, capabilities);
 }
 

packages/mcp-server/src/stdio.ts

@@ -1,12 +1,11 @@
 import { StdioServerTransport } from '@modelcontextprotocol/sdk/server/stdio.js';
-import { init, newMcpServer } from './server';
-import { Endpoint } from './tools';
+import { initMcpServer, newMcpServer } from './server';
 import { McpOptions } from './options';
 
-export const launchStdioServer = async (options: McpOptions, endpoints: Endpoint[]) => {
+export const launchStdioServer = async (options: McpOptions) => {
   const server = newMcpServer();
 
-  init({ server, endpoints });
+  initMcpServer({ server, mcpOptions: options });
 
   const transport = new StdioServerTransport();
   await server.connect(transport);

packages/mcp-server/tests/options.test.ts

@@ -29,15 +29,7 @@ describe('parseCLIOptions', () => {
       { type: 'operation', op: 'include', value: 'read' },
     ] as Filter[]);
 
-    // Default client capabilities
-    expect(result.capabilities).toEqual({
-      topLevelUnions: true,
-      validJson: true,
-      refs: true,
-      unions: true,
-      formats: true,
-      toolNameLength: undefined,
-    });
+    expect(result.capabilities).toEqual({});
 
     expect(result.list).toBe(false);
 
@@ -61,14 +53,7 @@ describe('parseCLIOptions', () => {
       { type: 'operation', op: 'exclude', value: 'write' },
     ] as Filter[]);
 
-    expect(result.capabilities).toEqual({
-      topLevelUnions: true,
-      validJson: true,
-      refs: true,
-      unions: true,
-      formats: true,
-      toolNameLength: undefined,
-    });
+    expect(result.capabilities).toEqual({});
 
     cleanup();
   });
@@ -99,7 +84,6 @@ describe('parseCLIOptions', () => {
       validJson: true,
       refs: true,
       unions: true,
-      formats: true,
       toolNameLength: 40,
     });
 
@@ -150,10 +134,7 @@ describe('parseCLIOptions', () => {
     expect(result.capabilities).toEqual({
       topLevelUnions: true,
       validJson: true,
-      refs: true,
       unions: true,
-      formats: true,
-      toolNameLength: undefined,
     });
 
     cleanup();
@@ -316,7 +297,7 @@ describe('parseQueryOptions', () => {
     ]);
 
     expect(result.client).toBe('cursor');
-    expect(result.includeDynamicTools).toBe(true);
+    expect(result.includeDynamicTools).toBe(undefined);
   });
 
   it('should override client from default options', () => {