AG-SKILL-EXTERNAL-INSTRUCTIONS: Untrusted External Instructions Fetch

What this rule means

A skill fetches its actual instructions or configuration dynamically at runtime from an external server, evading static analysis.

Why it matters

OWASP AST05: Fetching instructions externally means the skill's behavior can change completely after security review.

How to fix it

Bundle all instructions and configurations within the skill directory. Do not load them dynamically.

Detect it

pip install lucin
lucin scan .                  # all rules
lucin explain AG-SKILL-EXTERNAL-INSTRUCTIONS          # 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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