Addy's Agent Skills

// Overview

Agent Skills is a repository of engineering skills written by Addy Osmani that an AI coding agent loads as instructions. Each skill encodes a workflow, a quality gate or a set of practices — test-driven development, API and interface design, frontend UI engineering, code review — so the agent applies the same discipline on every task instead of improvising a different approach each session.

The pack is organised around the development lifecycle. Nine slash commands map onto the phases — `/spec` to define what to build, `/plan` to break it into small atomic tasks, `/build` to implement one slice at a time, `/test` to prove it works, `/constraints` to set the quality bar, `/review` before merge, `/webperf` to audit web performance, `/code-simplify` to cut complexity, and `/ship` to release. Skills also activate on their own based on what the agent is doing: designing an API triggers the API-design skill, building UI triggers the frontend skill.

It is agent-agnostic. The quickest route is the open `skills` CLI (`npx skills add addyosmani/agent-skills`), which the README says installs into 70+ agents, but the repository also documents native integrations for Claude Code plugins, Cursor, the Antigravity CLI, Gemini CLI, Codex, OpenCode, GitHub Copilot, Windsurf, Kiro and Command Code. The project is MIT-licensed.

// What it does

• Nine lifecycle slash commands — /spec, /plan, /build, /test, /constraints, /review, /webperf, /code-simplify, /ship
• `/build auto` generates the plan and implements every task in one approved pass, still test-driven and committing each task individually, pausing on failures
• Skills auto-activate from context — API work pulls in api-and-interface-design, UI work pulls in frontend-ui-engineering
• Installs into 70+ agents through the open skills CLI, or natively as a Claude Code plugin, Codex plugin, Gemini CLI skill or Antigravity plugin
• Individual skills can be installed on their own, e.g. code-review-and-quality, interview-me, test-driven-development
• MIT-licensed and readable — every skill is a plain Markdown file you can fork and edit

// Getting started

The fastest path works with any agent: the open skills CLI copies the skill files into whatever tool you already use.

npx skills add addyosmani/agent-skills            # install all 25 skills
npx skills add addyosmani/agent-skills --list     # browse before installing

npx skills add addyosmani/agent-skills --skill code-review-and-quality
npx skills add addyosmani/agent-skills --skill interview-me
npx skills add addyosmani/agent-skills --skill test-driven-development

/plugin marketplace add addyosmani/agent-skills
/plugin install agent-skills@addy-agent-skills

codex plugin marketplace add addyosmani/agent-skills
codex plugin add agent-skills@agent-skills

gemini skills install https://github.com/addyosmani/agent-skills.git --path skills

agy plugin install https://github.com/addyosmani/agent-skills.git

/spec        # define what to build
/plan        # break it into small atomic tasks
/build       # implement one slice at a time
/test        # prove it works
/review      # improve code health before merge
/ship        # release

Commands and code are distilled from the project's own documentation — always check the official repo for the latest.

// When to use it

• Give a coding agent a repeatable spec → plan → build → test → review → ship workflow instead of ad-hoc prompting
• Enforce a shared quality bar across a team whose members use different agents (Claude Code, Cursor, Codex, Copilot)
• Audit a site's web performance through the agent with /webperf rather than a separate tooling pass
• Borrow one practice — test-driven development or five-axis code review — without adopting the whole pack

// How Addy's Agent Skills compares

Addy's Agent Skills alongside other open-source agent skills & plugins tools AI/TLDR tracks, ranked by GitHub stars.