Skill Creator+
Guide for creating and reviewing effective skills.
When to Use
- Create skill, new skill, review skill, スキル作成
- Creating a new skill from scratch
- Updating or refactoring an existing skill
- Reviewing existing SKILL.md files → See references/skill-review-checklist.md
Core Principles
| Principle | Description |
|---|---|
| Concise is Key | Context window is shared. Only add what Claude doesn't already know. |
| Degrees of Freedom | Match specificity to task fragility (high/medium/low freedom) |
| Progressive Disclosure | Split into 3 levels: Metadata → Body → References |
Default assumption: Claude is already very smart. Challenge each piece: "Does this justify its token cost?"
Skill Structure
→ references/skill-structure.md for details
skill-name/
├── SKILL.md (required) # < 150 lines
├── scripts/ # Executable code
├── references/ # Documentation loaded on demand
└── assets/ # Output resources (templates, images)
→ See skill-structure.md > What NOT to Include for excluded files.
Creation Process
→ references/creation-process.md for details
| Step | Action |
|---|---|
| 1 | Understand with concrete examples |
| 2 | Plan reusable contents (scripts/references/assets) |
| 3 | Initialize: scripts/init_skill.py <name> --path <dir> |
| 4 | Edit skill and implement resources |
| 5 | Package: scripts/package_skill.py <path> |
| 6 | Iterate based on real usage |
SKILL.md Guidelines
Size Target
→ See skill-review-checklist.md > Line Count Target for size guidelines.
Quick rule: < 150 lines is good, > 300 lines must split to references.
Frontmatter
---
name: skill-name
description: "What it does. Use when [trigger conditions]. Triggers on 'keyword', 'phrase'."
---
Description must include: What the skill does AND when to trigger it.
⚠️ Why this matters: Skills may not be invoked if descriptions lack clear triggers. Include user phrases to improve routing accuracy.
| ✅ Good | ❌ Bad |
|---|---|
| Extract text and tables from PDF files, fill forms, merge documents. Use when working with PDF files or when the user mentions PDFs, forms, or document extraction. | Helps with documents |
| Set up book writing workspace. Triggers on "book writing", "執筆ワークスペース", "technical writing project". | Creates workspaces |
When to Use Section
Start with generic keywords users are likely to say:
## When to Use
- **PDF**, **extract text**, **form filling** ← Keywords first
- Processing documents with embedded images
- Filling PDF forms programmatically
Body
- Use imperative/infinitive form
- Link to references for details
- Keep essential workflow only
Review Checklist
→ references/skill-review-checklist.md
- [ ] SKILL.md under 150 lines?
- [ ] Description has trigger conditions?
- [ ] Details moved to references/?
- [ ] No README.md or auxiliary docs?
Key References
| Topic | Reference |
|---|---|
| Skill Structure | references/skill-structure.md |
| Creation Process | references/creation-process.md |
| Review Checklist | references/skill-review-checklist.md |
| Workflows | references/workflows.md |
| Output Patterns | references/output-patterns.md |
Done Criteria
- SKILL.md created and under 150 lines
- Frontmatter has name + description with trigger conditions
- Details moved to references/ (Progressive Disclosure)
- Review checklist passed