u/Dear_Lock_5280

I built a small open-source CLI for MCP server authors who use stdio transport.

The problem it checks for is simple but painful: any console.log(), print(), or other stdout text can corrupt the JSON-RPC stream. The tool runs a real initialize handshake, optionally sends a request like tools/list, allows stderr logs, and fails on stdout pollution, invalid JSON-RPC frames, crashes, timeouts, or missing responses.

Install/test:

npx --yes mcp-stdio-guard -- <your-server-command>

Repo:

https://github.com/1Utkarsh1/mcp-stdio-guard

I would love feedback from people building MCP servers: what other stdio/protocol failures should it catch?