node-mcp-poc

node-mcp-poc

A minimal Model Context Protocol server in Node.js/TypeScript. It runs over HTTP (Express + Streamable HTTP) by default, with stdio available as a fallback, and is attachable to Claude Code.

It exposes four demo tools:

| Tool | Input | Returns | | ----------- | --------------------------------- | ----------------------------------- | | add | { a: number, b: number } | the sum, e.g. 2 + 3 = 5 | | echo | { text: string } | the same text | | now | { timezone?: string } | current time (ISO + localized) | | fetch_url | { url: string, maxChars?: int } | HTTP GET body (JSON pretty-printed) |

Build

Requires Node.js 24 (see .nvmrc) and pnpm. Builds and tests run on Vite / Vitest.

pnpm install
pnpm build     # vite build -> build/index.js (server) + build/lambda.js (Lambda)

Run

The server reads its config from the environment (a .env file is loaded automatically — see .env.example):

| Variable | Default | Purpose | | --------------- | ------- | -------------------------------------------------- | | MCP_TRANSPORT | http | http (Express) or stdio | | PORT | 3219 | HTTP port; endpoint is http://localhost:PORT/mcp | | LOG_LEVEL | info | pino log level | | NODE_ENV | — | development pretty-prints HTTP logs |

pnpm start          # HTTP server on http://localhost:3219/mcp
pnpm start:stdio    # stdio transport instead

Attach to Claude Code

This repo ships a project-level .mcp.json pointing at the HTTP endpoint, so within this directory the server is picked up automatically once it's running:

{
    "mcpServers": {
        "node-poc": { "type": "http", "url": "http://localhost:3219/mcp" },
    },
}

Start the server (pnpm start), then start (or restart) a Claude Code session and try:

• "add 2 and 3"
• "echo hello"
• "what time is it in America/New_York"
• "fetch https://api.github.com/zen via node-poc"

Check it's connected with claude mcp list.

To register it from anywhere instead of relying on .mcp.json:

# HTTP (server must already be running)
claude mcp add --transport http node-poc http://localhost:3219/mcp

# or stdio (Claude Code launches the process for you)
claude mcp add node-poc -- node /ABSOLUTE/PATH/TO/node-mcp-poc/build/index.js

Remove it with:

claude mcp remove node-poc

Develop / debug

pnpm dev        # rebuild + node --watch
pnpm test       # vitest run
pnpm test:watch # vitest (watch mode)
pnpm typecheck  # tsc --noEmit
pnpm smoke      # build + stdio client smoke test (scripts/smoke.mjs)
pnpm smoke:http # HTTP client smoke test (scripts/smoke-http.mjs)
pnpm logs       # tail logs/server.log through pino-pretty
pnpm inspect    # open the MCP Inspector against the server

Deploy

Deploying to AWS? See docs/README.md.

• Lambda (SAM CLI) — src/lambda.ts is a stateless variant of the server;

template.yaml deploys it on nodejs24.x behind a Function URL. pnpm sam:build && sam deploy --guided.

• Container (App Runner / ECS Fargate) — the prime target for the stateful

src/index.ts server (in-memory sessions + SSE), which Lambda can't host.

Notes

• The tools are defined once in src/mcp.ts (createMcpServer) and shared by

both entry points: src/index.ts (long-running, stateful HTTP/stdio) and src/lambda.ts (stateless, for Lambda).

• In HTTP mode each MCP session gets its own server instance, keyed by the

Mcp-Session-Id header; logs go to stdout (pretty-printed when NODE_ENV=development).

• In stdio mode stdout is reserved for the JSON-RPC wire, so logs go to

stderr and logs/server.log (view with pnpm logs).

• Add new tools in src/mcp.ts via server.registerTool(...).