chore(internal): refactor flag parsing for MCP servers and add debug flag

Author: stainless-app[bot]

packages/mcp-server/package.json

@@ -40,6 +40,7 @@
     "fuse.js": "^7.1.0",
     "jq-web": "https://github.com/stainless-api/jq-web/releases/download/v0.8.8/jq-web.tar.gz",
     "morgan": "^1.10.0",
+    "morgan-body": "^2.6.9",
     "qs": "^6.14.1",
     "typescript": "5.8.3",
     "yargs": "^17.7.2",

packages/mcp-server/src/http.ts

@@ -4,6 +4,7 @@ import { McpServer } from '@modelcontextprotocol/sdk/server/mcp';
 import { StreamableHTTPServerTransport } from '@modelcontextprotocol/sdk/server/streamableHttp.js';
 import express from 'express';
 import morgan from 'morgan';
+import morganBody from 'morgan-body';
 import { McpOptions } from './options';
 import { ClientOptions, initMcpServer, newMcpServer } from './server';
 import { parseAuthHeaders } from './headers';
@@ -76,14 +77,26 @@ const del = async (req: express.Request, res: express.Response) => {
 export const streamableHTTPApp = ({
   clientOptions = {},
   mcpOptions,
+  debug,
 }: {
   clientOptions?: ClientOptions;
   mcpOptions: McpOptions;
+  debug: boolean;
 }): express.Express => {
   const app = express();
   app.set('query parser', 'extended');
   app.use(express.json());
-  app.use(morgan('combined'));
+
+  if (debug) {
+    morganBody(app, {
+      logAllReqHeader: true,
+      logAllResHeader: true,
+      logRequestBody: true,
+      logResponseBody: true,
+    });
+  } else {
+    app.use(morgan('combined'));
+  }
 
   app.get('/', get);
   app.post('/', post({ clientOptions, mcpOptions }));
@@ -92,16 +105,20 @@ export const streamableHTTPApp = ({
   return app;
 };
 
-export const launchStreamableHTTPServer = async (options: McpOptions, port: number | string | undefined) => {
-  const app = streamableHTTPApp({ mcpOptions: options });
-  const server = app.listen(port);
+export const launchStreamableHTTPServer = async (params: {
+  mcpOptions: McpOptions;
+  debug: boolean;
+  port: number | string | undefined;
+}) => {
+  const app = streamableHTTPApp({ mcpOptions: params.mcpOptions, debug: params.debug });
+  const server = app.listen(params.port);
   const address = server.address();
 
   if (typeof address === 'string') {
     console.error(`MCP Server running on streamable HTTP at ${address}`);
   } else if (address !== null) {
     console.error(`MCP Server running on streamable HTTP on port ${address.port}`);
   } else {
-    console.error(`MCP Server running on streamable HTTP on port ${port}`);
+    console.error(`MCP Server running on streamable HTTP on port ${params.port}`);
   }
 };

packages/mcp-server/src/index.ts

@@ -21,7 +21,11 @@ async function main() {
       await launchStdioServer();
       break;
     case 'http':
-      await launchStreamableHTTPServer(options, options.port ?? options.socket);
+      await launchStreamableHTTPServer({
+        mcpOptions: options,
+        debug: options.debug,
+        port: options.port ?? options.socket,
+      });
       break;
   }
 }

packages/mcp-server/src/options.ts

@@ -4,6 +4,7 @@ import { hideBin } from 'yargs/helpers';
 import z from 'zod';
 
 export type CLIOptions = McpOptions & {
+  debug: boolean;
   transport: 'stdio' | 'http';
   port: number | undefined;
   socket: string | undefined;
@@ -15,33 +16,33 @@ export type McpOptions = {
 
 export function parseCLIOptions(): CLIOptions {
   const opts = yargs(hideBin(process.argv))
-    .option('tools', {
+    .option('debug', { type: 'boolean', description: 'Enable debug logging' })
+    .option('no-tools', {
       type: 'string',
       array: true,
       choices: ['code', 'docs'],
-      description: 'Use dynamic tools or all tools',
+      description: 'Tools to explicitly disable',
     })
-    .option('no-tools', {
+    .option('port', {
+      type: 'number',
+      default: 3000,
+      description: 'Port to serve on if using http transport',
+    })
+    .option('socket', { type: 'string', description: 'Unix socket to serve on if using http transport' })
+    .option('tools', {
       type: 'string',
       array: true,
       choices: ['code', 'docs'],
-      description: 'Do not use any dynamic or all tools',
+      description: 'Tools to explicitly enable',
     })
     .option('transport', {
       type: 'string',
       choices: ['stdio', 'http'],
       default: 'stdio',
       description: 'What transport to use; stdio for local servers or http for remote servers',
     })
-    .option('port', {
-      type: 'number',
-      default: 3000,
-      description: 'Port to serve on if using http transport',
-    })
-    .option('socket', {
-      type: 'string',
-      description: 'Unix socket to serve on if using http transport',
-    })
+    .env('MCP_SERVER')
+    .version(true)
     .help();
 
   const argv = opts.parseSync();
@@ -57,6 +58,7 @@ export function parseCLIOptions(): CLIOptions {
 
   return {
     ...(includeDocsTools !== undefined && { includeDocsTools }),
+    debug: !!argv.debug,
     transport,
     port: argv.port,
     socket: argv.socket,