AG-011: Tool Description Injection / Poisoning

What this rule means

Tool descriptions contain patterns consistent with prompt injection or jailbreak.

Why it matters

Invariant Labs (2025): demonstrated tool poisoning against WhatsApp and GitHub MCP servers.

How to fix it

Pin tool descriptions, sanitize before use, monitor for changes.

Detect it

pip install lucin
lucin scan .                  # all rules
lucin explain AG-011          # this rule, in your terminal

Findings carry a file:line and, where the rule supports it, a witness path showing the flow that triggered it. Precision and recall for the whole rule set, with the commands that regenerate them, are on the benchmarks page — and the gaps are on limits.

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