Initial Checks
Description
Hi All, I am actually following the mcp tutorials from MCP official documentation. After creating the server . It is throwing error saying "Received exception from stream: 1 validation error for JSONRPCMessage " . I tried to create it simple server from different tutorial . The same error is repeating .
[02/15/26 20:14:37] ERROR Received exception from stream: 1 validation error for JSONRPCMessage server.py:700 Invalid JSON: EOF while parsing a value at line 2 column 0 [type=json_invalid, input_value='\n', input_type=str] For further information visit https://errors.pydantic.dev/2.12/v/json_invalid {"method":"notifications/message","params":{"level":"error","logger":"mcp.server.exception_handler","data":"Internal Server Error"},"jsonrpc":"2.0"}
Example Code
from typing import Any
import httpx
from mcp.server.fastmcp import FastMCP
# Initialize FastMCP server
mcp = FastMCP("weather")
# Constants
NWS_API_BASE = "https://api.weather.gov"
USER_AGENT = "weather-app/1.0"
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:
return None
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")}
"""
@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)
@mcp.tool()
async def get_forecast(latitude: float, longitude: float) -> str:
"""Get weather forecast for a location.
Args:
latitude: Latitude of the location
longitude: Longitude of the location
"""
# 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)
def main():
# Initialize and run the server
mcp.run(transport="stdio")
if __name__ == "__main__":
main()Python & MCP Python SDK
python - 3.14
mcp version - 1.26.0
Initial Checks
Description
Hi All, I am actually following the mcp tutorials from MCP official documentation. After creating the server . It is throwing error saying "Received exception from stream: 1 validation error for JSONRPCMessage " . I tried to create it simple server from different tutorial . The same error is repeating .
[02/15/26 20:14:37] ERROR Received exception from stream: 1 validation error for JSONRPCMessage server.py:700 Invalid JSON: EOF while parsing a value at line 2 column 0 [type=json_invalid, input_value='\n', input_type=str] For further information visit https://errors.pydantic.dev/2.12/v/json_invalid {"method":"notifications/message","params":{"level":"error","logger":"mcp.server.exception_handler","data":"Internal Server Error"},"jsonrpc":"2.0"}Example Code
Python & MCP Python SDK