Weather MCP Server

Implementation Reference

• tools/weather_tools.py:21-44 (handler)

  The asynchronous handler function implementing the core logic of the 'get_forecast' tool. It retrieves weather forecast data from the NWS API using latitude and longitude, formats the first 5 periods, and returns a string summary.

  async def get_forecast(latitude: float, longitude: float) -> str:
      url = f"{NWS_API_BASE}/points/{latitude},{longitude}"
      data = await make_nws_request(url)
  
      if not data:
          return "Unable to fetch forecast data for this location."
      
      forecast_url = data["properties"]["forecast"]
      forecast_data = await make_nws_request(forecast_url)
  
      if not forecast_data:
          return "Unable to fetch detailed forecast."
  
      periods = forecast_data["properties"]["periods"]
      forecasts = []
      for period in periods[:5]:
          forecast = f"""
              {period['name']}:
              Temperature: {period['temperature']}°{period['temperatureUnit']}
              Wind: {period['windSpeed']} {period['windDirection']}
              Forecast: {period['detailedForecast']}
          """
          forecasts.append(forecast)
      return "\n---\n".join(forecasts)

• tools/weather_tools.py:20-20 (registration)

  The @mcp.tool() decorator registers the get_forecast function as an MCP tool, using its name as the tool identifier.

  @mcp.tool()

• utils/weather_utils.py:7-16 (helper)

  Utility function to make asynchronous HTTP requests to the NWS API, handling errors and headers. Called twice in the get_forecast handler.

  async def make_nws_request(url: str) -> dict[str, Any] | None:
      headers = {"User-Agent": USER_AGENT, "Accept": "application/geo+json"}
      async with httpx.AsyncClient() as client:
          try:
              response = await client.get(url, headers=headers, timeout=30.0)
              response.raise_for_status()
              return response.json()
          except Exception:
              return None

• utils/weather_utils.py:4-4 (helper)

  Constants used by the get_forecast tool: base URL for NWS API and User-Agent header.

  NWS_API_BASE = "https://api.weather.gov"