MCP Server Demo

Quick demo to show the local MCP client/server example.

Prerequisites

• Node.js (16+)

Install (if you haven't already):

npm install

Run the demo (spawns multiple clients):

npm run demo

Or run a single client with a custom name:

node client.js Stephen

What it does

• server.js is a minimal newline-delimited JSON tool server exposing say_hello.
• client.js spawns server.js, sends { tool: 'say_hello', args: { name } }, and logs the response.
• demo.js runs several client.js instances concurrently to showcase multiple requests and responses.

Web demo

• Start the web demo server and open the UI in your browser:

npm run web
# then open http://localhost:3000 in a browser

The web UI lets you type a name and click "Send say_hello" to demonstrate the MCP request/response flow over WebSocket.

Calling external APIs from the server

• You can make the server call an external HTTP API via the call_api tool.

Usage (CLI/stdin): send a request like:

{ "id": 1, "tool": "call_api", "args": { "path": "/status" } }

If EXTERNAL_API_BASE is set in the environment the path will be resolved relative to that base. Example (PowerShell):

$env:EXTERNAL_API_BASE = 'https://api.example.com'
echo '{ "id": 1, "tool": "call_api", "args": { "path": "/status" } }' | node server.js

The server will return a JSON response containing status, headers, and body (parsed JSON when possible).

Want a web-based demo or a demo that uses the installed @modelcontextprotocol/sdk transport? I can implement that next.