MCP Weather SSE Server

Instructions

Args:
    latitude: Latitude of the location
    longitude: Longitude of the location

Implementation Reference

• weather.py:194-229 (handler)

  The main execution logic for the 'get_forecast' tool. This async function is decorated with @mcp.tool(), which also serves as registration. It fetches the forecast grid point data from NWS API, retrieves the detailed forecast, and formats the next 5 periods into a string response.

  @mcp.tool()
  async def get_forecast(latitude: float, longitude: float) -> str:
      """Get weather forecast for a location using NWS (US only).
  
      Args:
          latitude: Latitude of the location
          longitude: Longitude of the location
      """
      print(f"get_forecast called with lat: {latitude}, lon: {longitude}", file=sys.stderr)
      # First get the forecast grid endpoint
      points_url = f"{NWS_API_BASE}/points/{latitude},{longitude}"
      points_data = await make_nws_request(points_url)
  
      if not points_data:
          return "Unable to fetch forecast data for this location."
  
      # Get the forecast URL from the points response
      forecast_url = points_data["properties"]["forecast"]
      forecast_data = await make_nws_request(forecast_url)
  
      if not forecast_data:
          return "Unable to fetch detailed forecast."
  
      # Format the periods into a readable forecast
      periods = forecast_data["properties"]["periods"]
      forecasts = []
      for period in periods[:5]:  # Only show next 5 periods
          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)

• weather.py:195-201 (schema)

  Input/output schema defined by function signature (latitude: float, longitude: float) -> str and docstring describing parameters.

  async def get_forecast(latitude: float, longitude: float) -> str:
      """Get weather forecast for a location using NWS (US only).
  
      Args:
          latitude: Latitude of the location
          longitude: Longitude of the location
      """

• weather.py:24-38 (helper)

  Supporting utility function used by get_forecast to make authenticated HTTP requests to the NWS API endpoints.

  async def make_nws_request(url: str) -> dict[str, Any] | None:
      """Make a request to the NWS API with proper error handling."""
      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 as e:
              print(f"NWS API error: {e}", file=sys.stderr)
              return None