createMcpExpressRouter

createMcpExpressRouter(server: McpServer, options?: CreateMcpExpressRouterOptions): Router

Mount the router on the path that the host connects to.

import express from "express";
import { createMcpExpressRouter } from "ng-mcp-ui/server";

const app = express();
app.use(express.json());
app.use("/mcp", createMcpExpressRouter(createMcpServer()));

app.use(express.json()) must run before the router. The handler reads req.body.

Mount the router before the SSR catch-all route of Angular. A catch-all that runs first answers /mcp with your application shell.

Options

Option	Type	Default	Purpose
cors	boolean	true	Applies a permissive CORS layer. A host fetches this endpoint from another origin, therefore the default is true. Set false if your app already controls CORS for this path.
errorMiddleware	ErrorRequestHandler[]	[]	Express error handlers for this router. They run before the built-in JSON-RPC error handler.

Errors

The router has a built-in error handler. It answers with a JSON-RPC 500 response.

Put your own handlers in errorMiddleware to log an error, or to change it. The handlers run in sequence, before the built-in handler.

app.use(
  "/mcp",
  createMcpExpressRouter(server, {
    errorMiddleware: [
      (err, req, res, next) => {
        logger.error(err);
        next(err);
      },
    ],
  }),
);

• A handler that sends a response stops the built-in handler.
• A handler that calls next(err) passes the error to the built-in handler.

No app-level middleware

The server has no use() method and no useOnError() method. It gives you a router, and it does not own an Express app.

Put HTTP middleware on your own app, around the router:

app.use("/mcp", rateLimit, createMcpExpressRouter(server));

For MCP-level concerns that must run on each transport, use mcpMiddleware instead.

Related

• createViewAssetRouter
• requireBearerAuth
• mcpMiddleware