Evaluate Claude Skills: Triggering, Output, Safety

Trigger evals

A skill that never triggers is dead. A skill that triggers everywhere is dangerous. Build a small prompt set with three groups: tasks that should activate the skill, tasks that sound adjacent but should not, and tasks that try to lure the skill outside its stated boundaries.

Write prompts in the language real users use. If users say "make this match our board deck," the description should probably mention board decks, not only "executive presentation system."

Output evals

Triggering is only the first test. The output should meet the stated definition of done. If the skill creates a document, inspect format and content. If it reviews code, inspect finding quality and file references. If it runs a script, inspect command output and failure behavior.

Use fixtures whenever possible. A known input with a known desired output gives you a stable regression test when you change the description or procedure.

Safety evals

Safety evals should test predictable pressure points: secrets, destructive commands, private data, regulated claims, and external services. A finance-analysis skill should not invent compliance claims. A deploy skill should not push production changes without confirmation.

The goal is not to make the skill paranoid. The goal is to make the stop conditions explicit enough that the agent can preserve momentum on ordinary work and pause on risky work.

Keep a tiny eval log

Keep the log close to the skill while iterating. Once the skill is stable, promote the most important prompts to a formal test harness or review checklist.

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