Glossary · Phase 9 · Model Context Protocol
Rug pull
A server quietly changing its tools after you approved them. Pinning a fingerprint of each tool catches it.
A landlord could hand you a fair lease, and then swap the pages after you've signed. A server can look harmless on the day you approve it, then change its tool definitions later: a new description, a new parameter, a tool that now does something else. That's a rug pull.
Try it now
All tool definitions and results are untrusted input.
Learn it properly
MCP security · Tool poisoning, rug pulls, confused deputies and local-server risks. About 40 minutes.
Other terms from the same lesson
- tool poisoning: Hiding instructions for the model inside a tool's description, often where the user can't see them.
- typosquatting: Publishing a malicious package under a name one letter off a popular one, hoping people install it by mistake.
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