Most teams install an MCP server and hope it works.

That is how you get 3 AM pages.

An MCP server is a bridge between AI agents and your tools. It can crash, leak data, or silently return garbage. If your AI agent relies on it, your whole pipeline breaks.

MCP means Model Context Protocol (standard tool link).

Do not only test startup. Test behavior and permissions too.

This post is the checklist I run on every MCP server before it touches production.

The three-layer test stack

Layer What it catches Tool

Discovery Missing tools, broken metadata MCP Inspector

Behavior Silent failures, wrong output pytest smoke tests

Security Over-permissions, data leaks Permission audit

Layer 1: Discovery with MCP Inspector

MCP Inspector is the official debugging tool.…