Weather MCP Server

Instructions

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

Implementation Reference

• weather.py:58-75 (handler)

  The handler function implementing the 'get_alerts' tool. It is registered via the @mcp.tool() decorator, fetches active weather alerts for the specified US state using the NWS API, handles errors, formats the alerts, and returns a formatted string.

  @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)
      """
      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 no 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)

• weather.py:17-29 (helper)

  Helper function that makes asynchronous HTTP requests to the NWS API with proper headers, timeout, and error handling. Used by the get_alerts handler.

  """Make a request to the NWS API with proper error handling."""
  headers = {"User-Agent": USER_AGENT, "Accept": "application/geo+json"}
  # Creates an HTTP client using httpx library (async alternative to requests)
  # async with ensures client closes properly
  async with httpx.AsyncClient() as client:
      try:
          response = await client.get(url, headers=headers, timeout=30.0)
          response.raise_for_status()  # Raises error if status code is 4xx/5xx
          return response.json()
      # If anything fails, returns None instead of crashing
      except Exception:
          return None

• weather.py:33-43 (helper)

  Helper function that formats a single weather alert feature into a human-readable string, extracting key properties like event, area, severity, etc. Used by the get_alerts handler.

  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")}
  """