Weather Server

Instructions

Args:
    state: Two-letter US state code (e.g. CA, NY, TX)

Implementation Reference

• weather.py:105-127 (handler)

  The handler function for the 'get_alerts' tool. It validates the US state code, fetches active weather alerts from the National Weather Service API, formats them using helper functions, and returns a formatted string response.

  @mcp.tool()
  async def get_alerts(state: str) -> str:
      """Get weather alerts for a US state.
  
      Args:
          state: Two-letter US state code (e.g. CA, NY, TX)
      """
      state = state.upper().strip()
      
      if not validate_state_code(state):
          return f"Error: '{state}' is not a valid US state code. Please use a 2-letter code (e.g., CA, NY, TX)."
      
      url = f"{NWS_API_BASE}/alerts/active/area/{state}"
      data = await make_nws_request(url)
  
      if not data or "features" not in data:
          return f"Unable to fetch alerts for {state}. The location may not be supported or the service is unavailable."
  
      if not data["features"]:
          return f"No active weather alerts for {state}."
  
      alerts = [format_alert(feature) for feature in data["features"]]
      return f"Weather Alerts for {state}:\n\n" + "\n---\n".join(alerts)

• weather.py:93-102 (helper)

  Helper function to format individual weather alert data into a human-readable string format.

  def format_alert(feature: dict) -> str:
      """Format an alert feature into a readable string."""
      props = feature["properties"]
      return f"""
  Event: {props.get('event', 'Unknown')}
  Area: {props.get('areaDesc', 'Unknown')}
  Severity: {props.get('severity', 'Unknown')}
  Description: {props.get('description', 'No description available')}
  Instructions: {props.get('instruction', 'No specific instructions provided')}
  """

• weather.py:23-26 (helper)

  Helper function to validate if the provided state code is a valid two-letter US state abbreviation. Relies on the US_STATES constant.

  def validate_state_code(state: str) -> bool:
      """Validate that the state code is a valid 2-letter US state code."""
      return state.upper() in US_STATES

• weather.py:73-92 (helper)

  Helper function to make HTTP requests to the National Weather Service API with proper headers, timeout, and comprehensive error handling.

  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 httpx.HTTPStatusError as e:
              if e.response.status_code == 404:
                  return None
              return None
          except (httpx.RequestError, httpx.TimeoutException):
              return None
          except Exception:
              return None

• weather.py:105-105 (registration)

  The @mcp.tool() decorator registers the get_alerts function as an MCP tool in the FastMCP server.

  @mcp.tool()