🌤️ Weather MCP Server (Node.js)

A remote MCP (Model Context Protocol) server built on Node.js / Express. It exposes the get_weather tool via Streamable HTTP transport, letting MCP clients such as Claude Code query the current weather of any city in real time.

Weather data comes from wttr.in — free, no registration, no API key required.

✨ Features

• 🛰️ Remote MCP service: Implements Streamable HTTP transport based on the official @modelcontextprotocol/sdk, supporting both JSON and SSE response modes

• 🌆 Global city support: Pass a city name directly (e.g. Beijing, Tokyo, Paris) to look up local weather

• 🔌 Full session management: Automatically generates/validates Mcp-Session-Id, supporting session creation, reuse, and termination (DELETE)

• 🧩 Single-file ready to use: No database, zero configuration files, just one server.js to get started

Related MCP server: MCP Weather Server — Demo

📦 Requirements

• Node.js ≥ 18 (built-in fetch, no extra dependencies)

🚀 Quick Start

# 1. 安装依赖
npm install

# 2. 启动服务(默认端口 3000)
npm start

# 后台运行(日志写入 logs/server.log)
npm run start:bg

Once started successfully, the service address is:

http://localhost:3000/mcp

Common scripts

🔌 Configuring an MCP client

In Claude Code or another MCP client that supports Streamable HTTP, register the service as a remote MCP server.

Claude Code

Add it via the MCP server list (/mcp → Add → HTTP):

{
  "type": "http",
  "url": "http://localhost:3000/mcp"
}

JSON configuration file method

{
  "mcpServers": {
    "weather": {
      "type": "http",
      "url": "http://localhost:3000/mcp"
    }
  }
}

🧰 Provided tools

get_weather

Get the current weather for a specified city.

Parameters

Example response

当前 Beijing 的天气是晴(Sunny),温度 28°C(体感 30°C),湿度 45%,风速 12 km/h。

⚙️ Implementation notes

• Session isolation: Each session holds its own Server + transport instance (the SDK's connect() only supports one transport), associated via the Mcp-Session-Id request header.

• New session flow: A POST without Mcp-Session-Id is treated as an initialization request; the server generates a session ID and returns it via the Mcp-Session-Id response header (explicitly exposed to browser clients via CORS exposedHeaders).

• Compatibility handling: A GET SSE probe request without a session ID keeps an open SSE stream open (instead of returning 404/400), so clients like Claude Code can continue with the POST initialization flow.

• Reliable error responses: When the weather API call fails, it returns a result with isError: true instead of crashing the entire request.

🗂️ Project structure

.
├── server.js          # 全部服务逻辑(单文件)
├── package.json       # 项目配置与脚本
├── logs/              # 运行时日志(已被 .gitignore 忽略)
└── LICENSE            # MIT 许可证

📄 License

MIT