🌤️ Weather MCP Server

Your first MCP server — connects any MCP-compatible AI (like Claude) to real-time weather data via OpenWeatherMap.

Built with TypeScript. No fluff, just the fundamentals.

What is MCP?

MCP (Model Context Protocol) is an open standard that lets AI models call external tools and APIs. Instead of the AI guessing the weather, it calls your server, which calls the real API and returns live data.

Claude → calls tool → your MCP server → OpenWeatherMap API → real data back to Claude

What This Server Does

Exposes three tools:

| Tool | Input | Output | |------|-------|--------| | get_weather | city name | temperature, humidity, wind, visibility | | get_forecast | city name | 5-day forecast | | compare_weather | two city names | side by side comparison |

Prerequisites

• Node.js v18 or higher
• Claude Desktop installed
• Free OpenWeatherMap API key

Project Structure

weather-mcp/
├── src/
│   └── index.ts        ← your server code (edit this)
├── dist/
│   └── index.js        ← compiled output (auto-generated, don't edit)
├── node_modules/       ← installed packages (auto-generated)
├── package.json        ← project dependencies
├── tsconfig.json       ← TypeScript compiler config
└── README.md

Setup

1. Clone the repo

git clone https://github.com/YOUR_USERNAME/weather-mcp.git
cd weather-mcp

2. Install dependencies

npm install

3. Add your API key

Open src/index.ts and replace line 16:

const API_KEY = "YOUR_API_KEY_HERE";

with your actual OpenWeatherMap API key.

4. Compile TypeScript

npx tsc

5. Test the server runs

node dist/index.js

You should see:

Weather MCP server running — 3 tools ready: get_weather, get_forecast, compare_weather

Press Ctrl+C to stop.

Connect to Claude Desktop

macOS — open this file:

~/Library/Application Support/Claude/claude_desktop_config.json

Windows — open this file:

%APPDATA%\Claude\claude_desktop_config.json

Paste this — replace the path with your actual project path:

macOS/Linux:

{
  "mcpServers": {
    "weather": {
      "command": "node",
      "args": ["/absolute/path/to/weather-mcp/dist/index.js"]
    }
  }
}

Windows:

{
  "mcpServers": {
    "weather": {
      "command": "node",
      "args": ["C:\\Users\\YourName\\weather-mcp\\dist\\index.js"]
    }
  }
}

Fully quit Claude Desktop (system tray → right click → Quit) and reopen it.

Try It

Open Claude Desktop and type any of these:

What is the weather in Tokyo?
What is the forecast for Mumbai this week?
Is it hotter in Dubai or London right now?

tsconfig.json

Create this file in your project root:

{
  "compilerOptions": {
    "target": "ES2017",
    "module": "Node16",
    "moduleResolution": "Node16",
    "outDir": "./dist",
    "strict": false,
    "esModuleInterop": true,
    "skipLibCheck": true
  },
  "include": ["src/**/*"]
}

How It Works

Every MCP server has exactly three parts:

1. Create the server

const server = new McpServer({ name: "weather-server", version: "1.0.0" })

2. Register tools

server.tool("get_weather", "description", { inputs }, async () => {
  // call your API here
  return { content: [{ type: "text", text: result }] }
})

3. Connect and start

const transport = new StdioServerTransport()
await server.connect(transport)

That's it. Every MCP server you ever build follows this exact same pattern.

Dependencies

| Package | Purpose | |---------|---------| | @modelcontextprotocol/sdk | MCP protocol — handles all communication with Claude | | zod | Input validation + schema generation so Claude knows what each tool expects | | typescript | Type safety, compiles to JavaScript that Node can run |

Extending This Server

Want to add more tools? Copy any server.tool() block and change the name, description, inputs, and API call inside.

Ideas:

• get_uv_index — UV index for a city
• get_air_quality — air pollution data
• get_sunrise_sunset — sunrise and sunset times

License

MIT — use it, modify it, build on it.