MCP Stdio Guard
Supports UIby 1Utkarsh1
Catch stdout pollution and handshake failures in MCP stdio servers before they crash your client.
What it does
MCP Stdio Guard is a runtime diagnostic tool designed to validate the health and protocol compliance of MCP stdio servers. Because MCP servers use stdout as their primary communication channel, any accidental debug logs, print statements, or banners can corrupt the JSON-RPC stream, leading to cryptic client failures. This tool acts as a proxy and validator to ensure your server is truly 'silent' and compliant.
Tools
As a diagnostic utility, this tool does not expose MCP tools itself but validates the following on target servers:
- Initialize Handshake: Verifies the server completes the protocol lifecycle correctly.
- Capability Probing: Checks that advertised tools, resources, and prompts are actually responsive.
- Stdout Validation: Scans for non-JSON frames that pollute the transport stream.
- Static Analysis: Scans source code for risky
console.logorprintcalls.
Installation
Run your server behind the guard using npx:
npx mcp-stdio-guard -- node ./server.js
Supported hosts
Confirmed for use with any MCP client supporting stdio transport, specifically tested for Claude Desktop and Cursor.
Quick install
npx mcp-stdio-guard -- <your-server-command>Information
- Pricing
- free
- Published
- 5/23/2026
