Use This Skill is a directory of 1,400+ agent skills for Claude Code, Codex, Cursor and other coding agents, with proofs of what each one changes. Most skill lists rank by GitHub stars, which tell you who found a skill but not what it does. Each proven skill here is run through Claude twice on the same brief, once without the skill and once with it, and both results are published as live pages you can click through, with the model and the skill's exact commit recorded so anyone can repeat the comparison. Searching and installing skills is free, with a one-line install command for every listing. One proof is free to try, and Pro unlocks every proof for a single $99 payment.