Give a Codex Skill a Clear Trigger
A reusable skill needs a clear reason to be selected. “Helps with documents” is too broad to distinguish an invoice check from a presentation rewrite.
Write a description that names the job, the expected input and a useful exclusion. For example: validate a synthetic invoice CSV against a supplied column contract; do not calculate tax or send invoices. Then give Codex several matching and nonmatching requests and observe when it selects the skill.
Keep the full procedure in the skill's instructions, with references for details needed only during execution. The documented skill mechanism loads more detail when the skill is chosen. That saves carrying every procedure into every task, but it makes the selection description part of the behavior you need to test.
