Agent Skills is an open-source collection of engineering skills that encode the workflows, quality gates, and best practices senior engineers use, packaged so AI coding agents follow them consistently. It exposes seven slash commands mapped to the development lifecycle: /spec, /plan, /build, /test, /review, /code-simplify, and /ship, each activating the right skills automatically. A /build auto mode can generate a plan and implement every task in a single approved, autonomous pass while keeping each task test-driven and committed individually, pausing on failures or risky steps. Skills also activate automatically based on what the developer is doing, bringing structure and verification to agent-driven coding.