version: "1.0.1" name: creating-skills description: Guide for creating Claude Code skills following Anthropic's official best practices. Use when user wants to create a new skill, build a skill, write SKILL.md, update an existing skill, or needs skill creation guidelines. Provides structure, frontmatter fields, naming conventions, and new features like dynamic context injection and subagent execution.

Creating skills

Guide for creating Claude Code skills following Anthropic's official best practices.

Quick start

# 1. Create skill directory
mkdir -p ~/.claude/skills/<skill-name>
 
# 2. Create SKILL.md with frontmatter
cat > ~/.claude/skills/<skill-name>/SKILL.md << 'EOF'
---
name: <skill-name>
description: <What it does>. Use when <trigger phrases>. <Key capabilities>.
---
 
# <Skill title>
 
<Instructions for the skill workflow>
EOF
 
# 3. Add optional resources as needed
mkdir -p ~/.claude/skills/<skill-name>/{scripts,references,assets}

SKILL.md structure

Frontmatter (YAML between --- markers)

Invocation control matrix

Description formula

<What it does>. Use when <trigger phrases>. <Key capabilities>.

Include action verbs ("create", "handle"), user intent ("wants to", "needs to"), and domain keywords users would say.

Directory structure

skill-name/
├── SKILL.md              # Required: instructions (keep under 500 lines)
├── scripts/              # Optional: executable code (deterministic, token-efficient)
├── references/           # Optional: docs loaded into context on demand
└── assets/               # Optional: files used in output, NOT loaded into context
                          #   (templates, images, fonts, boilerplate)

Progressive disclosure (3-level loading)

1. Metadata (name + description) - always in context (~100 tokens per skill)
2. SKILL.md body - loaded when skill triggers (keep under 5k words)
3. Bundled resources - loaded as needed by Claude

Reference supporting files from SKILL.md so Claude knows they exist. Keep references one level deep. For files over 100 lines, include a table of contents.

Scripts vs references vs assets

Only create scripts when they add value: complex multi-step processing, repeated code generation, deterministic reliability. Not for single-command wrappers.

Dynamic features

Context injection

Inject shell command output into skill content before loading:

## Recent commits
!`git log --oneline -5 2>/dev/null`

The output replaces the directive when the skill loads.

String substitutions

Pass arguments to skills invoked via /skill-name arg1 arg2:

Subagent execution

Run a skill in isolated context with context: fork:

---
name: deep-research
description: Research a topic thoroughly.
context: fork
agent: Explore
---

Degrees of freedom

Match specificity to the task's fragility:

Naming conventions

• Lowercase, hyphens between words, max 64 chars
• Styles: gerund (processing-pdfs), noun phrase (github-pr-creation), prefixed group (github-pr-*)

Important rules

• ALWAYS write descriptions that include WHAT + WHEN triggers + capabilities
• ALWAYS keep SKILL.md under 500 lines, split to references when approaching
• ALWAYS reference bundled files from SKILL.md so Claude discovers them
• NEVER duplicate info between SKILL.md and reference files
• NEVER create wrapper scripts for single commands
• NEVER include extraneous files (README.md, CHANGELOG.md, INSTALLATION_GUIDE.md, QUICK_REFERENCE.md)
• NEVER explain things Claude already knows (standard libraries, common tools, basic patterns)

References

• references/official_best_practices.md - Principles, anti-patterns, quality checklist, testing
• references/skill_examples.md - Concrete skill examples with new features