Weather MCP Server

Implementation Reference

• tools/weather_tools.py:6-18 (handler)

  The core handler function for the 'get_alerts' tool. It fetches active weather alerts for a specified state using the National Weather Service (NWS) API, formats them, and returns a string summary.

  @mcp.tool()
  async def get_alerts(state: str) -> str:
      url = f"{NWS_API_BASE}/alerts/active/area/{state}"
      data = await make_nws_request(url)
  
      if not data or "features" not in data:
          return "Unable to fetch alerts or not alerts found"
  
      if not data["features"]:
          return "No active alerts for this state."
      
      alerts = [format_alert(feature) for feature in data["features"]]
      return "\n---\n".join(alerts)

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

  Helper utility to perform asynchronous HTTP requests to the NWS API, handling errors and returning JSON data or None.

  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:17-25 (helper)

  Helper function to format a single weather alert feature into a human-readable string.

  def format_alert(feature: dict) -> str:
      props = feature["properties"]
      return f"""
          Event: {props.get('event', 'Unknown')}
          Area: {props.get('areaDesc', 'Unknown')}
          Severity: {props.get('severity', 'Unknown')}
          Descripton: {props.get('description', 'No description')}
          Instructions: {props.get('instruction', 'No specific instruction')}
      """

• tools/weather_tools.py:4-6 (registration)

  The FastMCP instance is created and the tool is registered via the @mcp.tool() decorator.

  mcp = FastMCP("weather")
  
  @mcp.tool()