My MCP Tools Broke Silently; So I Built a Lockfile for MCP

The Problem I run AI agents that depend on MCP servers. One morning, everything broke. No error message. No warning. Just silent failures. After 4 hours of debugging, I found it: the MCP server updated and renamed a parameter from location to city . My agent was still sending location . The server returned a cryptic -32602 error. The MCP spec has 9,400+ servers and 97 million SDK downloads per month. But it has zero per-tool versioning . When a server changes its tool schemas, nothing tells you