agents-skills

name	agents-skills
description	Reference for creating AI agent skills with SKILL.md structure. Use when building or improving modular skill files for Claude Code or Codex.

Agent Skills - Meta Reference

This skill provides the definitive reference for creating, organizing, and maintaining agent skills. Use this when building new skills or improving existing skill architecture.

Quick Reference

Component	Purpose	Required
SKILL.md	Main reference file with frontmatter	Yes
scripts/	Executable code (prefer running)	Optional
references/	Documentation (loaded on-demand)	Recommended
assets/	Output files (templates, icons)	Optional
data/sources.json	Curated external links	Recommended

Cross-Platform: Agent Skills are designed to be portable across runtimes (Claude Code, Codex CLI, Gemini CLI, VS Code Copilot).

Skill Structure

skills/
	└── skill-name/
	    ├── SKILL.md           # Main reference (required)
	    ├── scripts/           # Executable code (Python/Bash) - prefer running; read only to patch/review
	    │   └── validate.py
	    ├── references/        # Documentation loaded into context on-demand
	    │   ├── patterns.md
	    │   └── examples.md
    ├── assets/            # Files for OUTPUT (templates, icons, fonts)
    │   └── template.html
    └── data/
        └── sources.json   # External references

Directory purposes:

• scripts/ - Executable code; prefer running scripts and consuming output (read only when you need to modify/review)
• references/ - Documentation loaded into context when the agent needs it
• assets/ - Files used in generated output (not loaded into context)

Notes:

• Prefer executing scripts instead of pasting large code into context; read scripts only when you need to modify or review them.

SKILL.md Template

---
name: skill-name
description: One-line description of what this skill provides and when to use it (include trigger keywords here)
---

# Skill Name - Quick Reference

Brief overview of the skill's purpose and value.

## Quick Reference

| Task | Tool/Method | When to Use |
|------|-------------|-------------|
| Task 1 | Tool A | Context for usage |

## Scope (Optional)

Keep this brief; the primary trigger mechanism is the frontmatter `description`.

## Core Concepts

### Concept 1

Explanation with code example:

\`\`\`language
code example
\`\`\`

### Concept 2

Additional patterns...

## Navigation

**Resources**
- [references/skill-patterns.md](references/skill-patterns.md) - Common patterns
- [references/skill-validation.md](references/skill-validation.md) - Validation criteria

**Related Skills**
- [../agents-subagents/SKILL.md](../agents-subagents/SKILL.md) - Agent creation

Progressive Disclosure

Skills use progressive disclosure to optimize token usage:

Layer	Content	Token Cost
Discovery	Name + description only	~50 tokens
Activation	Full SKILL.md body	2K-5K tokens
Execution	scripts/, references/, assets/	On-demand

Pattern: SKILL.md provides overview -> Resources load only when needed

Limits: Keep SKILL.md under 500 lines (<5K tokens)

When to Split Content

Keep in SKILL.md	Move to references/
Decision trees	Full API references
Quick commands	Step-by-step tutorials
Common patterns	Edge case handling
1-2 code examples	Complete implementations

Frontmatter Specification

Field	Type	Required	Purpose
name	string	Yes	Kebab-case, must match folder name
description	string	Yes	Primary trigger — runtime reads this to decide invocation
argument-hint	string	No	Autocomplete hint shown in / menu (e.g. [issue-number])
disable-model-invocation	bool	No	true prevents auto-triggering; user must invoke with /
user-invocable	bool	No	false hides from / menu; still loads as background context
allowed-tools	string	No	Comma-separated tool allowlist (e.g. Read, Grep, Glob)
context	string	No	Set to fork to run skill body in a subagent
agent	string	No	Subagent type when context: fork (e.g. Explore, Plan)
model	string	No	Model override (opus, sonnet, haiku)
hooks	object	No	Lifecycle hooks scoped to this skill
license	string	No	License identifier
compatibility	string	No	Platform/version notes (1-500 chars)
metadata	object	No	Author, version, mcp-server

See references/frontmatter-reference.md for full specification, examples, and string substitutions.

Name rules:

• Use kebab-case: ai-llm, not AI_LLM_Engineering
• Match folder name exactly
• Be specific: software-backend not backend
• No claude or anthropic in names (reserved words)
• No XML angle brackets (< >) in any frontmatter value

Description rules (PRIMARY TRIGGER):

• The runtime uses descriptions to decide which skills to auto-invoke
• Format: [What it does]. Use when [trigger phrases].
• Target ~150 chars when library has 50+ skills (budget: 2% of context window, ~16K chars shared across ALL skill descriptions)
• Include key technologies/concepts as trigger keywords
• Single-line YAML only — no multiline >-

String substitutions (usable in skill body):

• $ARGUMENTS / $ARGUMENTS[N] / $N — user-provided arguments from /skill-name arg1 arg2
• ${CLAUDE_SESSION_ID} — current session identifier
• ${CLAUDE_SKILL_DIR} — absolute path to this skill's directory

Dynamic context injection: Use !`command` in the skill body to inject command output at load time.

Skill Categories

Category	Prefix	Examples
AI/ML	ai-	ai-llm, ai-ml-data-science
Software	software-	software-backend, software-frontend
Operations	ops-	ops-devops-platform
Data	data-	data-lake-platform, data-sql-optimization
Quality	qa-	qa-debugging, qa-docs-coverage
Developer Tools	dev-	dev-api-design, dev-git-commit-message, dev-workflow-planning
Product	product-	product-management, docs-ai-prd
Document	document-	document-pdf, document-xlsx
Testing	testing-, qa-testing-	qa-testing-playwright, qa-testing-strategy
Marketing	marketing-	marketing-social-media, marketing-seo
Agents/Tools	agents-	agents-subagents, agents-skills, agents-hooks

sources.json Schema

{
  "metadata": {
    "title": "Skill Name - Sources",
    "description": "Brief description",
    "last_updated": "YYYY-MM-DD",
    "skill": "skill-name"
  },
  "category_name": [
    {
      "name": "Resource Name",
      "url": "https://example.com/docs",
      "description": "What this covers",
      "add_as_web_search": true
    }
  ]
}

Categories should group logically:

• official_documentation
• tutorials
• community_resources
• tools_and_libraries

Quality Checklist

SKILL VALIDATION CHECKLIST

Frontmatter:
[ ] name matches folder name (kebab-case)
[ ] description is concise and actionable

Structure:
[ ] SKILL.md under 500 lines (split into references/ if needed)
[ ] references/ for detailed content
[ ] data/sources.json with curated links

Content:
[ ] Quick reference table at top
[ ] Frontmatter `description` includes trigger keywords
[ ] Code examples are copy-paste ready
[ ] Related skills linked at bottom

Quality:
[ ] >40% operational content (code, tables, checklists)
[ ] <50% prose paragraphs
[ ] All URLs are live (no 404s)
[ ] Sources updated within 6 months

Multi-Tech vs Single-Tech Skills

Single-Tech Skill

software-backend/
├── SKILL.md              # Node.js focus
└── references/
    └── nodejs-patterns.md

Multi-Tech Skill

software-backend/
├── SKILL.md              # Overview + decision tree
├── references/
│   ├── nodejs-patterns.md
│   ├── go-patterns.md
│   ├── rust-patterns.md
│   └── python-patterns.md
└── assets/
    ├── nodejs/
    ├── go/
    ├── rust/
    └── python/

Navigation

Resources

• references/anthropic-skills-guide.md - Anthropic's official skill-building guide (distilled)
• references/frontmatter-reference.md - Complete frontmatter field specification
• references/skill-patterns.md - Common skill patterns
• references/skill-validation.md - Validation criteria
• data/sources.json - Official documentation links

Related Skills

• ../agents-subagents/SKILL.md - Agent creation
• ../agents-hooks/SKILL.md - Hook automation
• ../agents-mcp/SKILL.md - MCP server integration

Fact-Checking

• Use web search/web fetch to verify current external facts, versions, pricing, deadlines, regulations, or platform behavior before final answers.
• Prefer primary sources; report source links and dates for volatile information.
• If web access is unavailable, state the limitation and mark guidance as unverified.