Every team using an AI coding agent eventually builds a private collection of “the good prompts.”

The payment-review prompt. The release checklist. The incident-triage runbook. The one that makes the agent check tests before it confidently edits the first plausible file.

They start as a useful chat message, then become a 70-line paste, then get copied into AGENTS.md , then get shortened until the important constraints disappear.

That is the point where a prompt should become a skill.

Not because a SKILL.md file is magical. It is useful because it forces a workflow to answer five questions that a pasted prompt usually leaves implicit:

When should this run?

What inputs are required?

What sequence must the agent follow?

What may it not do without approval?

What observable evidence says the work is complete?

The fifth question is the one that changes outcomes.…