agent-skills is a production-grade engineering skills library for AI coding agents, led by Addy Osmani. It breaks the full lifecycle from spec and plan to build, verify, review, and ship into 25 skills and nine slash commands, using anti-rationalization tables and required evidence to stop agents from cutting corners. This guide covers what it is, its features, how to install and trigger it across Claude Code, Cursor, Codex, Copilot and seventy plus hosts, plus its MIT license and team adoption.