fix(mcp): initialize SDK lazily to avoid failing the connection on init errors

Author: stainless-app[bot]

packages/mcp-server/src/http.ts

@@ -24,28 +24,17 @@ const newServer = async ({
   const stainlessApiKey = getStainlessApiKey(req, mcpOptions);
   const server = await newMcpServer(stainlessApiKey);
 
-  try {
-    const authOptions = parseClientAuthHeaders(req, false);
+  const authOptions = parseClientAuthHeaders(req, false);
 
-    await initMcpServer({
-      server: server,
-      mcpOptions: mcpOptions,
-      clientOptions: {
-        ...clientOptions,
-        ...authOptions,
-      },
-      stainlessApiKey: stainlessApiKey,
-    });
-  } catch (error) {
-    res.status(401).json({
-      jsonrpc: '2.0',
-      error: {
-        code: -32000,
-        message: `Unauthorized: ${error instanceof Error ? error.message : error}`,
-      },
-    });
-    return null;
-  }
+  await initMcpServer({
+    server: server,
+    mcpOptions: mcpOptions,
+    clientOptions: {
+      ...clientOptions,
+      ...authOptions,
+    },
+    stainlessApiKey: stainlessApiKey,
+  });
 
   return server;
 };

packages/mcp-server/src/index.ts

@@ -24,7 +24,7 @@ async function main() {
       await launchStreamableHTTPServer({
         mcpOptions: options,
         debug: options.debug,
-        port: options.port ?? options.socket,
+        port: options.socket ?? options.port,
       });
       break;
   }

packages/mcp-server/src/server.ts

@@ -56,15 +56,33 @@ export async function initMcpServer(params: {
     error: logAtLevel('error'),
   };
 
-  let client = new Dedalus({
-    ...{ environment: (readEnv('DEDALUS_ENVIRONMENT') || undefined) as any },
-    logger,
-    ...params.clientOptions,
-    defaultHeaders: {
-      ...params.clientOptions?.defaultHeaders,
-      'X-Stainless-MCP': 'true',
-    },
-  });
+  let _client: Dedalus | undefined;
+  let _clientError: Error | undefined;
+  let _logLevel: 'debug' | 'info' | 'warn' | 'error' | 'off' | undefined;
+
+  const getClient = (): Dedalus => {
+    if (_clientError) throw _clientError;
+    if (!_client) {
+      try {
+        _client = new Dedalus({
+          ...{ environment: (readEnv('DEDALUS_ENVIRONMENT') || undefined) as any },
+          logger,
+          ...params.clientOptions,
+          defaultHeaders: {
+            ...params.clientOptions?.defaultHeaders,
+            'X-Stainless-MCP': 'true',
+          },
+        });
+        if (_logLevel) {
+          _client = _client.withOptions({ logLevel: _logLevel });
+        }
+      } catch (e) {
+        _clientError = e instanceof Error ? e : new Error(String(e));
+        throw _clientError;
+      }
+    }
+    return _client;
+  };
 
   const providedTools = selectTools(params.mcpOptions);
   const toolMap = Object.fromEntries(providedTools.map((mcpTool) => [mcpTool.tool.name, mcpTool]));
@@ -82,6 +100,21 @@ export async function initMcpServer(params: {
       throw new Error(`Unknown tool: ${name}`);
     }
 
+    let client: Dedalus;
+    try {
+      client = getClient();
+    } catch (error) {
+      return {
+        content: [
+          {
+            type: 'text' as const,
+            text: `Failed to initialize client: ${error instanceof Error ? error.message : String(error)}`,
+          },
+        ],
+        isError: true,
+      };
+    }
+
     return executeHandler({
       handler: mcpTool.handler,
       reqContext: {
@@ -94,24 +127,29 @@ export async function initMcpServer(params: {
 
   server.setRequestHandler(SetLevelRequestSchema, async (request) => {
     const { level } = request.params;
+    let logLevel: 'debug' | 'info' | 'warn' | 'error' | 'off';
     switch (level) {
       case 'debug':
-        client = client.withOptions({ logLevel: 'debug' });
+        logLevel = 'debug';
         break;
       case 'info':
-        client = client.withOptions({ logLevel: 'info' });
+        logLevel = 'info';
         break;
       case 'notice':
       case 'warning':
-        client = client.withOptions({ logLevel: 'warn' });
+        logLevel = 'warn';
         break;
       case 'error':
-        client = client.withOptions({ logLevel: 'error' });
+        logLevel = 'error';
         break;
       default:
-        client = client.withOptions({ logLevel: 'off' });
+        logLevel = 'off';
         break;
     }
+    _logLevel = logLevel;
+    if (_client) {
+      _client = _client.withOptions({ logLevel });
+    }
     return {};
   });
 }