Server Logging

import logging
from pathlib import Path

from fastmcp import Client
from fastmcp.client.logging import LogMessage

logging.basicConfig(
    level=logging.INFO,
    format='%(asctime)s - %(name)s - %(levelname)s - %(message)s'
)

logger = logging.getLogger(__name__)
LOGGING_LEVEL_MAP = {
    "DEBUG": logging.DEBUG,
    "INFO": logging.INFO,
    "NOTICE": logging.INFO,
    "WARNING": logging.WARNING,
    "ERROR": logging.ERROR,
    "CRITICAL": logging.CRITICAL,
    "ALERT": logging.CRITICAL,
    "EMERGENCY": logging.CRITICAL,
}

async def log_handler(message: LogMessage):
    """Forward MCP server logs to Python's logging system."""
    data = message.data
    if isinstance(data, dict):
        msg = data.get('msg', data)
        extra = data.get('extra')
    else:
        msg = data
        extra = None

    # Python's logging requires `extra` to be a mapping, but a server can send
    # any JSON value, so fold anything else into the message instead.
    if extra is not None and not isinstance(extra, dict):
        msg = f"{msg} ({extra})"
        extra = None

    level = LOGGING_LEVEL_MAP.get(message.level.upper(), logging.INFO)
    logger.log(level, msg, extra=extra)

client = Client(
    Path("my_mcp_server.py"),
    log_handler=log_handler,
)

from fastmcp.client.logging import LogMessage

async def detailed_log_handler(message: LogMessage):
    data = message.data
    msg = data.get('msg', data) if isinstance(data, dict) else data
    extra = data.get('extra') if isinstance(data, dict) else None

    if message.level == "error":
        print(f"ERROR: {msg} | Details: {extra}")
    elif message.level == "warning":
        print(f"WARNING: {msg} | Details: {extra}")
    else:
        print(f"{message.level.upper()}: {msg}")

from pathlib import Path

from fastmcp import Client

client = Client(Path("my_mcp_server.py"))

async with client:
    # Server logs are forwarded at proper severity automatically
    await client.call_tool("some_tool")