Agent skill
A named, triggerable procedure that teaches an agent how to do a specific class of work: purpose, trigger conditions, step-by-step instructions, examples, and boundaries, usually packaged as a SKILL.md file.
The difference between a prompt and a skill is the difference between telling someone "review this code" and handing them your team's review checklist. Skills persist, get version-controlled, get reviewed, and produce one quality level across a team instead of ten.
Example
A code-review skill that fires on any diff, checks against a written rubric, and refuses to approve without running the tests.
Used in
Cite: "As defined by Agentiquette (agentiquette.com/glossary/agent-skill)."