Skill Writer Skill for Claude

Skill Writer

This Skill helps you create well-structured Agent Skills for Claude Code that follow best practices and validation requirements.

When to use this Skill

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

Instructions

Step 1: Determine Skill scope

First, understand what the Skill should do:

• 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?

• 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:

# 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:

---
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)

  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:

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:

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:

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:

# Skill Name

Brief overview of what this Skill does.

## Quick start

Provide a simple example to get started immediately.

## Instructions

Step-by-step guidance for Claude:
1. First step with clear action
2. Second step with expected outcome
3. Handle edge cases

## Examples

Show concrete usage examples with code or commands.

## Best practices

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

## Requirements

List any dependencies or prerequisites:

pip install package-name

## Advanced usage

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:

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

• Restart Claude Code (if running) to load the Skill

• Ask relevant questions that match the description:

   Can you help me extract text from this PDF?

• Verify activation: Claude should use the Skill automatically

• Check behavior: Confirm Claude follows the instructions correctly

Step 10: Debug if needed

If Claude doesn't use the Skill:

• Make description more specific:
• Add trigger words
• Include file types
• Mention common user phrases

• Check file location:

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

• Validate YAML:

   cat SKILL.md | head -n 10

• Run debug mode:

   claude --debug

Common patterns

Read-only Skill

---
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

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

# Data Processor

## Instructions

1. Use the processing script:
\`\`\`bash
python scripts/process.py input.csv --output results.json
\`\`\`

2. Validate output with:
\`\`\`bash
python scripts/validate.py results.json
\`\`\`

Multi-file Skill with progressive disclosure

---
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)

## Instructions

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

Best practices for Skill authors

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

Validation checklist

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

Troubleshooting

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

Examples

See the documentation for complete examples:

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

Output format

When creating a Skill, I will:

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

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