Most "AI coding" advice stops at the prompt. addyosmani/agent-skills goes after the process: it packages the habits senior engineers use (spec first, small tasks, tests as proof, review before merge) as skills your agent follows every time. Here is how to install it in Claude Code and what you get.

What it is

The README describes production-grade engineering skills for AI coding agents, organized around a lifecycle: define, plan, build, verify, review, ship. Nine slash commands map to those phases:

  • /spec: spec before code
  • /plan: small, atomic tasks
  • /build: one slice at a time
  • /test: tests are proof
  • /constraints: decide the quality bar once
  • /review: improve code health
  • /webperf: measure before you optimize
  • /code-simplify: clarity over cleverness
  • /ship: faster is safer

Skills also activate on their own. Per the README, designing an API triggers api-and-interface-design and building UI triggers frontend-ui-engineering.

Install in Claude Code

The marketplace route, straight from the README:

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

If the install fails with git@github.com: Permission denied (publickey), the README gives two fixes. Add the full HTTPS URL when you add the marketplace, or rewrite GitHub SSH URLs to HTTPS once:

git config --global url."https://github.com/".insteadOf git@github.com:

To try it from a local clone instead:

git clone https://github.com/addyosmani/agent-skills.git claude --plugin-dir /path/to/agent-skills

One naming catch: Claude Code already has a built-in /review, so use the namespaced form /agent-skills:review.

Not on Claude Code?

The README lists a one-command path for 70+ agents (Claude Code, Cursor, Codex, Copilot, Cline) through the open skills CLI:

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

Or pick single skills:

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

The README warns that a per-skill install copies only the skill folder, not the shared references/ directory, so supplementary checklists will be missing. Install the whole repo if you want them. For Gemini CLI the command is gemini skills install https://github.com/addyosmani/agent-skills.git --path skills.

A first session

Try the lifecycle on a small feature rather than a rewrite:

  1. Run /spec and describe the feature. Let the agent ask questions before it writes anything.
  2. Run /plan and check that the tasks are small enough to review one at a time.
  3. Run /build for the first slice, then /test.
  4. Run /agent-skills:review before you merge.

The README also mentions /build auto, which plans once, asks for your approval, then implements every task in one pass. It says each task is still test-driven and committed individually, and that it pauses on failures or risky steps.

Who it is for

Anyone whose agent jumps straight to code and leaves you the cleanup. If you already have a strict team process, treat the skills as a starting point and edit them.

What we did not verify

  • We followed the README and did not run this end to end for this post.
  • The skill count and commands may change, so check the repo before you rely on them.

For a step-by-step version, see our agent-skills page and the spec, plan, build walkthrough. More like it are in best AI repos for coding agent skills.

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