Weather MCP Server for Claude

This repository implements a Model Context Protocol (MCP) server for Claude. It exposes weather-related tools via FastMCP over stdio, using the National Weather Service (NWS) API for data.

Project Structure

weather/
├── clients/
│   ├── __init__.py
│   └── nws_client.py
├── formatters/
│   ├── __init__.py
│   └── alert_formatter.py
├── services/
│   ├── __init__.py
│   └── weather_service.py
├── tools/
│   ├── __init__.py
│   └── weather_tools.py
├── models/
│   ├── __init__.py
│   └── responses.py
├── config.py
├── logging_config.py
├── main.py
├── pyproject.toml
└── README.md

Features

• MCP server for Claude using FastMCP
• get_alerts(state) tool for active weather alerts
• get_forecast(latitude, longitude) tool for forecast data
• Simple, maintainable service and client separation

Requirements

• Python 3.10 or higher
• uv installed and available at the full path used by Claude
• mcp and httpx dependencies installed in the Python environment

Running the Server Locally

From the repository root:

cd /Users/dinukakasun/Documents/MCP/weather
/Users/dinukakasun/.local/bin/uv --directory /Users/dinukakasun/Documents/MCP/weather run main.py

or using the virtual environment Python if preferred:

/Users/dinukakasun/Documents/MCP/weather/.venv/bin/python main.py

The server should start and expose MCP tools on stdio.

Claude Desktop MCP Configuration

Update ~/Library/Application Support/Claude/claude_desktop_config.json so Claude launches this server with the correct executable path and working directory.

Example configuration:

{
  "mcpServers": {
    "weather": {
      "command": "/Users/dinukakasun/.local/bin/uv",
      "args": [
        "--directory",
        "/Users/dinukakasun/Documents/MCP/weather",
        "run",
        "main.py"
      ]
    }
  }
}

Why absolute paths matter

Claude desktop may not inherit your interactive shell PATH. Using the absolute uv path avoids startup failures caused by missing commands.

Example Claude Questions

Use these example prompts to exercise the MCP server:

• Get the current weather alerts for CA using get_alerts.
• Call get_forecast with latitude 37.7749 and longitude -122.4194.
• What are active alerts for NY?
• Provide a 5-period weather forecast for 40.7128, -74.0060.

Local Test Client

You can verify the MCP tools locally with a small Python client that starts the server and sends a request over stdio.

import asyncio
import json
import subprocess

async def run_request():
    proc = await asyncio.create_subprocess_exec(
        "/Users/dinukakasun/.local/bin/uv",
        "--directory",
        "/Users/dinukakasun/Documents/MCP/weather",
        "run",
        "main.py",
        stdin=subprocess.PIPE,
        stdout=subprocess.PIPE,
        stderr=subprocess.PIPE,
    )

    request = {
        "jsonrpc": "2.0",
        "id": 1,
        "method": "initialize",
        "params": {
            "protocolVersion": "2024-11-05",
            "capabilities": {},
            "clientInfo": {"name": "local-test", "version": "1.0.0"}
        }
    }

    stdout, stderr = await proc.communicate((json.dumps(request) + "\n").encode())
    print(stdout.decode())
    print(stderr.decode())

asyncio.run(run_request())

This confirms the server accepts MCP requests. For tool-specific tests, replace method with a valid tool name and pass params matching the tool signature.

Verifying the MCP Server

1. Start the server manually.
2. Confirm the process is running:

ps aux | grep "main.py" | grep -v grep

3. Confirm Claude is configured to use the same command and working directory.
4. If Claude still does not connect, use the absolute uv path in claude_desktop_config.json.

Notes

• The MCP server uses stdio transport, not a network HTTP endpoint.
• The entrypoint is main.py, not weather.py.
• The tools are registered in tools/weather_tools.py.

Reference

• Model Context Protocol Python server docs: https://modelcontextprotocol.io/docs/develop/build-server#python