Agent Skills: Reusable Prompts in Claude Code.

You'll walk away with

1. What a skill is, where it lives (personal ~/.claude/skills vs project .claude/skills), and how Claude Code matches one to a request
2. How to author a SKILL.md with name, description, and instructions that reliably trigger when the task comes up
3. Advanced fields: allowed-tools for restricting capabilities and model for routing to a specific Claude model
4. Progressive disclosure: keeping SKILL.md under 500 lines and linking to supporting files Claude reads only when needed
5. When to use skills versus CLAUDE.md, subagents, hooks, or MCP, and how they complement each other
6. How to share skills via repo commits, plugins, or enterprise managed settings, and how to troubleshoot when one does not trigger

Read these first

Lesson outline

Every lesson from Introduction to Agent Skills with our one-line simplification. The Skilljar course is the source; we summarize.

The course in 7 paragraphs

Skills exist because every Claude Code user eventually notices they are typing the same instructions over and over. Every PR review, you re-describe how you want feedback structured. Every commit, you remind Claude of your message format. Skills fix this by letting you write a markdown file once that Claude applies automatically the next time the task comes up. The mental model is npm install for Claude's task-specific knowledge: scoped, on-demand, version-controlled.

Mechanically a skill is a directory containing a SKILL.md. The file has YAML frontmatter declaring at minimum name and description, then markdown instructions below. The description is load-bearing: at startup Claude Code loads only the names and descriptions of every available skill (cheap, no token cost). When you make a request, Claude semantically matches your phrasing against those descriptions and loads the full body of the matching skill into context. You see a confirmation prompt before the load. Skills are inert until they match.

Skills live in two places: personal at ~/.claude/skills/<skill-name>/ (follows you across all projects on your machine) and project at .claude/skills/<skill-name>/ inside a repo (committed to git, shared with everyone who clones). When names conflict, the priority hierarchy is Enterprise → Personal → Project → Plugins. Use personal for your own commit-message style or PR-review preferences; use project for team standards like coding conventions, brand guidelines, or framework-specific debugging checklists. Restart Claude Code after creating or editing a skill so it picks up the change.

Advanced configuration unlocks the production-grade use cases. `allowed-tools` restricts which tools Claude can use while the skill is active; set [Read, Grep, Glob] for a code-review skill so the reviewer cannot edit files even if the prompt drifts. `model` lets a skill request a specific Claude model. Progressive disclosure is the technique that keeps skills efficient: keep SKILL.md under 500 lines, and put deep references, scripts, and assets in sibling files that Claude reads on demand. The trick: Claude can execute a script and consume only its output, never the script's source, so a 2,000-line tax-rules-by-state lookup costs zero context tokens until the output lands.

Skills versus everything else is the question every team asks and the exam loves to test. CLAUDE.md loads into every conversation; use it for project-wide always-on standards (TypeScript strict mode, never modify the schema). Skills load on demand; use them for task-specific expertise that would clutter every conversation if it lived in CLAUDE.md. Subagents run in an isolated context with their own tool access; use them when you want delegation, not knowledge injection. Hooks fire on events (file save, tool call); use them for automation, not reasoning. MCP provides external tools; a different category entirely from skills. The right setup combines all of them.

Sharing scales the value. A personal skill stays on your machine. A project skill gets committed alongside the code; the next teammate who clones the repo gets it free. Plugins package a set of related skills (plus optional commands and config) for distribution outside a single repo. Managed settings let an enterprise admin push a skill set to every user's Claude Code installation, with the highest priority in the hierarchy. The shape that emerges is: personal skills are your habits, project skills are your team's standards, plugin skills are community contributions, enterprise skills are policy.

Troubleshooting follows a predictable pattern. Run the skills validator first; it catches structural problems (missing frontmatter, wrong filename, directory shape) faster than any other technique. If a skill does not trigger, the description is almost always the cause; add the trigger phrases users actually type. If it does not load, check that SKILL.md lives inside a named directory and that the filename is exactly SKILL.md (case-sensitive). If the wrong skill activates, two descriptions are too similar; disambiguate. For runtime errors in skill scripts, check dependencies, file permissions (chmod +x), and use forward slashes in paths. The exam treats skills as a recognition problem more than a creation problem. You will see scenarios describing team pain (a brand-guidelines doc Claude keeps missing, a PR-review style that drifts) and be asked which Claude Code feature solves it. Skill is the right answer when the knowledge is task-specific and on-demand; CLAUDE.md when it should always apply; subagent when you want isolation; hook when an event triggers automation; MCP when you need an external system.

6 takeaways with cross-pillar bridges

How this maps to the CCA-F exam

Domains

D1 Agentic Architectures · D2 Tool Design + Integration

Blueprint

27% (D1) + 18% (D2)

What it advances

Direct prep for D1 task statements on Claude Code customization features and D2 questions on choosing the right primitive for the job. Skills appear in agent-skills-for-enterprise-km, agent-skills-for-developer-tooling, and agent-skills-with-code-execution scenarios.

2 hand-picked extras

These amplify the Skilljar course beyond what the course itself covers. Each was picked for a specific reason.

Concepts in this course

Where you'll see this in production

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