---

name: skill-authoring description: Best practices for writing Claude Code skills and agents. Use when creating, improving, or troubleshooting SKILL.md or agent files.

Skill and Agent Authoring Guide

Skill Writing Principles

1. Strong Descriptions

Good: "Analyze Rust code for unsafe blocks, justify each usage. Use when reviewing Rust code for safety." Bad: "Helps with Rust" (too vague)

Include trigger keywords users would naturally say.

2. Progressive Disclosure

• Keep SKILL.md under 500 lines
• Split large content into separate files
• SKILL.md is the table of contents, not the encyclopedia

3. Validation Loops

Always include verify-fix-repeat patterns:

Copy1. Run validator (script or checklist)
2. Fix issues
3. Re-validate
4. Only proceed when clean

4. File Organization

Copyskill-name/
├── SKILL.md           # Overview and workflow
├── REFERENCE.md       # Detailed docs (optional)
├── EXAMPLES.md        # Code examples (optional)
└── validate.sh        # Utility scripts (optional)

Agent Writing Principles

1. Proactive Invocation

Use phrases in description:

• "Use PROACTIVELY after..."
• "MUST BE USED when..."
• "Automatically invoke for..."

2. Tool Restrictions

Only specify tools if you need restrictions:

Copytools: Read, Grep, Glob # Read-only agent

Omit for full tool access.

3. Model Selection

• sonnet: Fast, efficient (default)
• opus: Complex reasoning
• inherit: Match main conversation
• haiku: Very fast, simple tasks

4. Skills Integration

Copyskills: rust-patterns, security-check

Agent loads these skills at startup.

Common Patterns

Research Agent

Copydescription: Deep codebase analysis. Use for complex refactoring planning.
tools: Read, Grep, Glob, Bash
model: opus

Review Agent

Copydescription: Code review specialist. Use PROACTIVELY after commits.
tools: Read, Grep, Glob
skills: code-standards, security-patterns

Fix Agent

Copydescription: Automated test fixer. Use when tests fail.
tools: Read, Edit, Bash
skills: test-patterns

Troubleshooting

Skill Not Loading

1. Check filename is exactly SKILL.md (case-sensitive)
2. Verify frontmatter starts on line 1 (no blank lines before ---)
3. Use spaces, not tabs in YAML
4. Run claude --debug to see errors

Skill Not Triggering

1. Add more keywords to description
2. Make description action-oriented
3. Test with explicit keywords from description

Agent Not Invoked

1. Add "PROACTIVELY" or "MUST BE USED" to description
2. Make description more specific
3. Explicitly mention: "Use the X agent to..."

Testing Checklist

• YAML frontmatter is valid
• Description includes trigger keywords
• Instructions are clear and actionable
• Examples are included
• Validation steps are defined
• File is under 500 lines (for skills)
• Runs with claude --debug without errors