Claude Code Skills & SKILL.md

Package your know-how as reusable skills: SKILL.md structure, descriptions that trigger, supporting scripts and references, testing, security review and team sharing, with validators and a script harness you can run.

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Syllabus

What Skills Are

1. The Problem Skills Solve
2. Anatomy of a Skill: Folder, SKILL.md, Frontmatter, Body
3. Progressive Disclosure: Why Skills Stay Cheap
4. Skills vs CLAUDE.md, Commands, Subagents, MCP and Hooks

Writing a Good SKILL.md

1. Choosing a Name and Scope
2. The Description: Your Most Important Sentence
3. Structuring the Body: Steps, Examples, Gotchas

Scripts, References and Templates

1. Folder Layout and Loading Rules
2. Keeping SKILL.md Short and Details in References
3. Scripts: Deterministic Work Inside a Skill
4. allowed-tools and Least Privilege

Where Skills Live and How They Run

1. Personal, Project and Plugin Skills
2. Automatic and Explicit Invocation
3. Sharing, Versioning and Maintaining Skills

Testing and Improving Skills

1. Testing Triggering With Should and Should-Not Prompts
2. Testing Scripts Like Normal Code
3. Improving From Real Transcripts

Security and Trust

1. The Risks of Third-Party Skills
2. A Review Checklist Before Installing or Merging a Skill
3. Writing Safe Skills: Secrets, Injection and Isolation

Patterns and Recipes

1. Checklist and Review Skills
2. "Look at It" Skills: Closing the Verification Loop
3. Template and Workflow Skills
4. Anti-Patterns and When Not to Use a Skill

Putting It Together

1. Case Study: A Release-Notes Skill for a Team
2. Revision: Cheat Sheet and Self-Check