Meta-Skill Guide: Creating Claude Code Custom Skills

Quick Reference

Architecture: Three-Level Progressive Loading

Level 1: Metadata (~100 tokens/skill)

---
name: skill-name
description: Brief description with usage triggers
---

• •Loaded at Claude Code startup
• •Critical for skill discovery

Level 2: Instructions (<5,000 tokens)

• •Main SKILL.md body content
• •Loaded when user request matches description
• •Optimal: Under 500 lines

Level 3: Resources (Unlimited)

• •Additional markdown files, scripts, templates
• •Loaded as needed via bash navigation
• •Scripts execute without loading code into context

File Structure

skill-name/
├── SKILL.md              # Main instructions (mandatory)
├── reference/            # Additional documentation
│   ├── advanced.md
│   └── api_reference.md
├── scripts/              # Executable code
│   └── validator.py
└── templates/            # Templates
    └── template.ext

YAML Frontmatter

Required:

---
name: skill-name
description: What skill does and when to use it. Include triggers and key terms.
---

Optional (Claude Code):

allowed-tools: ["Bash", "Read", "Write", "Edit"]
model: claude-sonnet-4-5-20250929

Naming Rules:

• •Max 64 chars, lowercase letters/numbers/hyphens
• •Use gerund form: processing-pdfs (not process-pdf)
• •Avoid vague names: helper, utils, documents

Skill Levels

Best Practices Summary

Top 10 DOs

1. •Keep SKILL.md under 500 lines
2. •Write descriptions in third person with triggers
3. •Use consistent terminology throughout
4. •Provide concrete examples with input/output pairs
5. •Implement validation loops (Create -> Validate -> Fix)
6. •Structure long files with table of contents
7. •Use checklists for complex tasks
8. •Solve problems in scripts, don't punt to Claude
9. •Justify all constants and magic numbers
10. •List required packages explicitly

Top 10 DON'Ts

1. •Reference time-sensitive information
2. •Use Windows-style paths (scripts\helper.py)
3. •Assume tools are pre-installed
4. •Use vague MCP tool references
5. •Provide too many equal options (decision paralysis)
6. •Create deeply nested references (one level max)
7. •Skip validation for quality tasks
8. •Mix inconsistent terminology
9. •Leave constants unexplained
10. •Assume subagent context from conversation

Full checklist: reference/best-practices.md

Subagent Integration Summary

When to Delegate

Key Constraints

• •NO conversation history access - each invocation is fresh
• •NO nested delegation - main agent orchestrates all
• •File artifacts for state transfer - save results to files
• •Explicit output format - prevent context overload

Orchestration Patterns

1. •Parallel - Independent tasks, single message, multiple Task calls
2. •Sequential - Dependent tasks, file artifacts between steps
3. •Hub-and-Spoke - Implementation + multiple reviewers
4. •Iterative - Architect -> Reviewer cycles

Full guide: reference/subagent-patterns.md

Domain Patterns Summary

Full patterns: reference/domain-patterns.md

Quality & Testing Summary

Build Evaluations First

1. •Run Claude WITHOUT skill on real tasks
2. •Create 3+ test scenarios
3. •Write minimal instructions to pass
4. •Iterate based on real behavior

Two-Claude Method

• •Claude A: Skill author
• •Claude B: Skill tester
• •Iterate based on where B struggles

Cross-Model Testing

• • Haiku (cost optimization)
• • Sonnet (standard)
• • Opus (complex tasks)

Full guide: reference/evaluation.md

Key Takeaways

Architecture

• •Three-level progressive loading: metadata -> instructions -> resources
• •Filesystem-based: bash navigation, scripts execute without loading
• •One level deep references only

Structure

• •SKILL.md under 500 lines
• •YAML: name (64 chars) + description (1024 chars, third person)
• •Forward slashes always, gerund naming

Subagents

• •Context isolation: NO history, NO memory
• •Main agent orchestrates all delegation
• •File artifacts for state transfer
• •90% improvement with parallel specialists

Distribution

• •Skills don't sync across surfaces
• •Claude Code: ~/.claude/skills/ or .claude/skills/
• •Share via git for teams

External References

Official Docs:

• •Skills Overview: https://docs.claude.com/en/docs/agents-and-tools/agent-skills/overview
• •Best Practices: https://docs.claude.com/en/docs/agents-and-tools/agent-skills/best-practices
• •Claude Code Skills: https://docs.claude.com/en/docs/claude-code/skills

GitHub Examples:

• •Anthropic Skills: https://github.com/anthropics/skills
• •Claude Cookbooks: https://github.com/anthropics/claude-cookbooks/tree/main/skills

Full links: reference/links.md

Version

v1.2.0 (December 2025) - Refactored to progressive disclosure pattern