mcp-logging-stdout-stder-mcp-server-using-stdio-transport-logs-to-stdout-vi-d7fdab02

THEN Never write to stdout in STDIO-based MCP servers as it corrupts JSON-RPC messages. Use a logging library targeting stderr or files, or explicitly write to stderr (e.g., print('...', file=sys.stderr) in Python or console.error() in TypeScript). For HTTP-based servers, stdout logging is safe.

import sys
print('Processing request', file=sys.stderr)
logging.info('Processing request')