MCP tools can silently change schema after approval — an open-source proxy now catches it
jgarg27 · reddit · 2026-09-09
A Redditor found that MCP tools can quietly change their description or schema after approval with nothing catching the drift: diffing the official filesystem server's July 2025 vs current version reveals changed descriptions, new tools, and searchfiles silently switching from substring to glob matching. He built mcp-provenance-proxy, a local stdio proxy that logs every call to a hash-chained, tamper-evident file and flags schema drift by severity. TypeScript, MIT, no cloud.
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