This skill should be used when the user says "create a check", "write a check", "add a check", "apply checks", "run checks", "/checks", "vulnerability pattern", "detection check", "check for common bugs", "scan with checks", or wants to create, apply, or manage simple vulnerability pattern files that agents use to find flaws. Checks are the simplest unit of agentic vulnerability detection — markdown files describing what to look for and how to assess matches. This skill is NOT for general code review or ad-hoc vulnerability analysis.