skill-writer

Use this Skill when:

• Creating a new Agent Skill
• Writing or updating SKILL.md files
• Designing skill structure and frontmatter
• Troubleshooting skill discovery issues
• Converting existing prompts or workflows into Skills

Step 1: Determine Skill scope

First, understand what the Skill should do:

1. Ask clarifying questions:

- What specific capability should this Skill provide?

- When should Claude use this Skill?

- What tools or resources does it need?

- Is this for personal use or team sharing?

1. Keep it focused: One Skill = one capability

- Good: "PDF form filling", "Excel data analysis"

- Too broad: "Document processing", "Data tools"

Step 2: Choose Skill location

Determine where to create the Skill:

Personal Skills (~/.claude/skills/):

• Individual workflows and preferences
• Experimental Skills
• Personal productivity tools

Project Skills (.claude/skills/):

• Team workflows and conventions
• Project-specific expertise
• Shared utilities (committed to git)

Step 3: Create Skill structure

Create the directory and files:

```bash

# Personal

mkdir -p ~/.claude/skills/skill-name

# Project

mkdir -p .claude/skills/skill-name

```

For multi-file Skills:

```

skill-name/

├── SKILL.md (required)

├── reference.md (optional)

├── examples.md (optional)

├── scripts/

│ └── helper.py (optional)

└── templates/

└── template.txt (optional)

```

Step 4: Write SKILL.md frontmatter

Create YAML frontmatter with required fields:

```yaml

---

name: skill-name

description: Brief description of what this does and when to use it

---

```

Field requirements:

• name:

- Lowercase letters, numbers, hyphens only

- Max 64 characters

- Must match directory name

- Good: pdf-processor, git-commit-helper

- Bad: PDF_Processor, Git Commits!

• description:

- Max 1024 characters

- Include BOTH what it does AND when to use it

- Use specific trigger words users would say

- Mention file types, operations, and context

Optional frontmatter fields:

• allowed-tools: Restrict tool access (comma-separated list)

```yaml

allowed-tools: Read, Grep, Glob

```

Use for:

- Read-only Skills

- Security-sensitive workflows

- Limited-scope operations

Step 5: Write effective descriptions

The description is critical for Claude to discover your Skill.

Formula: [What it does] + [When to use it] + [Key triggers]

Examples:

✅ Good:

```yaml

description: 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.

```

✅ Good:

```yaml

description: Analyze Excel spreadsheets, create pivot tables, and generate charts. Use when working with Excel files, spreadsheets, or analyzing tabular data in .xlsx format.

```

❌ Too vague:

```yaml

description: Helps with documents

description: For data analysis

```

Tips:

• Include specific file extensions (.pdf, .xlsx, .json)
• Mention common user phrases ("analyze", "extract", "generate")
• List concrete operations (not generic verbs)
• Add context clues ("Use when...", "For...")

Step 6: Structure the Skill content

Use clear Markdown sections:

```markdown

# Skill Name

Brief overview of what this Skill does.

Provide a simple example to get started immediately.

Step-by-step guidance for Claude:

1. First step with clear action
2. Second step with expected outcome
3. Handle edge cases

Show concrete usage examples with code or commands.

• Key conventions to follow
• Common pitfalls to avoid
• When to use vs. not use

List any dependencies or prerequisites:

```bash

pip install package-name

```

For complex scenarios, see [reference.md](reference.md).

```

Step 7: Add supporting files (optional)

Create additional files for progressive disclosure:

reference.md: Detailed API docs, advanced options

examples.md: Extended examples and use cases

scripts/: Helper scripts and utilities

templates/: File templates or boilerplate

Reference them from SKILL.md:

```markdown

For advanced usage, see [reference.md](reference.md).

Run the helper script:

\\\`bash

python scripts/helper.py input.txt

\\\`

```

Step 8: Validate the Skill

Check these requirements:

✅ File structure:

• [ ] SKILL.md exists in correct location
• [ ] Directory name matches frontmatter name

✅ YAML frontmatter:

• [ ] Opening --- on line 1
• [ ] Closing --- before content
• [ ] Valid YAML (no tabs, correct indentation)
• [ ] name follows naming rules
• [ ] description is specific and < 1024 chars

✅ Content quality:

• [ ] Clear instructions for Claude
• [ ] Concrete examples provided
• [ ] Edge cases handled
• [ ] Dependencies listed (if any)

✅ Testing:

• [ ] Description matches user questions
• [ ] Skill activates on relevant queries
• [ ] Instructions are clear and actionable

Step 9: Test the Skill

1. Restart Claude Code (if running) to load the Skill

1. Ask relevant questions that match the description:

```

Can you help me extract text from this PDF?

```

1. Verify activation: Claude should use the Skill automatically

1. Check behavior: Confirm Claude follows the instructions correctly

Step 10: Debug if needed

If Claude doesn't use the Skill:

1. Make description more specific:

- Add trigger words

- Include file types

- Mention common user phrases

1. Check file location:

```bash

ls ~/.claude/skills/skill-name/SKILL.md

ls .claude/skills/skill-name/SKILL.md

```

1. Validate YAML:

```bash

cat SKILL.md | head -n 10

```

1. Run debug mode:

```bash

claude --debug

```

Read-only Skill

```yaml

---

name: code-reader

description: Read and analyze code without making changes. Use for code review, understanding codebases, or documentation.

allowed-tools: Read, Grep, Glob

---

```

Script-based Skill

```yaml

---

name: data-processor

description: Process CSV and JSON data files with Python scripts. Use when analyzing data files or transforming datasets.

---

# Data Processor

1. Use the processing script:

\\\`bash

python scripts/process.py input.csv --output results.json

\\\`

1. Validate output with:

\\\`bash

python scripts/validate.py results.json

\\\`

```

Multi-file Skill with progressive disclosure

```yaml

---

name: api-designer

description: Design REST APIs following best practices. Use when creating API endpoints, designing routes, or planning API architecture.

---

# API Designer

Quick start: See [examples.md](examples.md)

Detailed reference: See [reference.md](reference.md)

1. Gather requirements
2. Design endpoints (see examples.md)
3. Document with OpenAPI spec
4. Review against best practices (see reference.md)

```

1. One Skill, one purpose: Don't create mega-Skills
2. Specific descriptions: Include trigger words users will say
3. Clear instructions: Write for Claude, not humans
4. Concrete examples: Show real code, not pseudocode
5. List dependencies: Mention required packages in description
6. Test with teammates: Verify activation and clarity
7. Version your Skills: Document changes in content
8. Use progressive disclosure: Put advanced details in separate files

Before finalizing a Skill, verify:

• [ ] Name is lowercase, hyphens only, max 64 chars
• [ ] Description is specific and < 1024 chars
• [ ] Description includes "what" and "when"
• [ ] YAML frontmatter is valid
• [ ] Instructions are step-by-step
• [ ] Examples are concrete and realistic
• [ ] Dependencies are documented
• [ ] File paths use forward slashes
• [ ] Skill activates on relevant queries
• [ ] Claude follows instructions correctly

Skill doesn't activate:

• Make description more specific with trigger words
• Include file types and operations in description
• Add "Use when..." clause with user phrases

Multiple Skills conflict:

• Make descriptions more distinct
• Use different trigger words
• Narrow the scope of each Skill

Skill has errors:

• Check YAML syntax (no tabs, proper indentation)
• Verify file paths (use forward slashes)
• Ensure scripts have execute permissions
• List all dependencies

See the documentation for complete examples:

• Simple single-file Skill (commit-helper)
• Skill with tool permissions (code-reviewer)
• Multi-file Skill (pdf-processing)

When creating a Skill, I will:

1. Ask clarifying questions about scope and requirements
2. Suggest a Skill name and location
3. Create the SKILL.md file with proper frontmatter
4. Include clear instructions and examples
5. Add supporting files if needed
6. Provide testing instructions
7. Validate against all requirements

The result will be a complete, working Skill that follows all best practices and validation rules.