Skill Builder

---
name: "Skill Builder"
description: "Create new Claude Code Skills with proper YAML frontmatter, progressive disclosure structure, and complete directory organization. Use when you need to build custom skills for specific workflows, generate skill templates, or understand the Claude Skills specification."
---

# Skill Builder

## What This Skill Does

Creates production-ready Claude Code Skills with proper YAML frontmatter, progressive disclosure architecture, and complete file/folder structure. This skill guides you through building skills that Claude can autonomously discover and use across all surfaces (Claude.ai, Claude Code, SDK, API).

## Prerequisites

- Claude Code 2.0+ or Claude.ai with Skills support
- Basic understanding of Markdown and YAML
- Text editor or IDE

## Quick Start

### Creating Your First Skill

```bash
# 1. Create skill directory (MUST be at top level, NOT in subdirectories!)
mkdir -p ~/.claude/skills/my-first-skill

# 2. Create SKILL.md with proper format
cat > ~/.claude/skills/my-first-skill/SKILL.md << 'EOF'
---
name: "My First Skill"
description: "Brief description of what this skill does and when Claude should use it. Maximum 1024 characters."
---

# My First Skill

## What This Skill Does
[Your instructions here]

## Quick Start
[Basic usage]
EOF

# 3. Verify skill is detected
# Restart Claude Code or refresh Claude.ai
```

---

## Complete Specification

### 📋 YAML Frontmatter (REQUIRED)

Every SKILL.md **must** start with YAML frontmatter containing exactly two required fields:

```yaml
---
name: "Skill Name"                    # REQUIRED: Max 64 chars
description: "What this skill does    # REQUIRED: Max 1024 chars
and when Claude should use it."       # Include BOTH what & when
---
```

#### Field Requirements

**`name`** (REQUIRED):
- **Type**: String
- **Max Length**: 64 characters
- **Format**: Human-friendly display name
- **Usage**: Shown in skill lists, UI, and loaded into Claude's system prompt
- **Best Practice**: Use Title Case, be concise and descriptive
- **Examples**:
  - ✅ "API Documentation Generator"
  - ✅ "React Component Builder"
  - ✅ "Database Schema Designer"
  - ❌ "skill-1" (not descriptive)
  - ❌ "This is a very long skill name that exceeds sixty-four characters" (too long)

**`description`** (REQUIRED):
- **Type**: String
- **Max Length**: 1024 characters
- **Format**: Plain text or minimal markdown
- **Content**: MUST include:
  1. **What** the skill does (functionality)
  2. **When** Claude should invoke it (trigger conditions)
- **Usage**: Loaded into Claude's system prompt for autonomous matching
- **Best Practice**: Front-load key trigger words, be specific about use cases
- **Examples**:
  - ✅ "Generate OpenAPI 3.0 documentation from Express.js routes. Use when creating API docs, documenting endpoints, or building API specifications."
  - ✅ "Create React functional components with TypeScript, hooks, and tests. Use when scaffolding new components or converting class components."
  - ❌ "A comprehensive guide to API documentation" (no "when" clause)
  - ❌ "Documentation tool" (too vague)

#### YAML Formatting Rules

```yaml
---
# ✅ CORRECT: Simple string
name: "API Builder"
description: "Creates REST APIs with Express and TypeScript."

# ✅ CORRECT: Multi-line description
name: "Full-Stack Generator"
description: "Generates full-stack applications with React frontend and Node.js backend. Use when starting new projects or scaffolding applications."

# ✅ CORRECT: Special characters quoted
name: "JSON:API Builder"
description: "Creates JSON:API compliant endpoints: pagination, filtering, relationships."

# ❌ WRONG: Missing quotes with special chars
name: API:Builder  # YAML parse error!

# ❌ WRONG: Extra fields (ignored but discouraged)
name: "My Skill"
description: "My description"
version: "1.0.0"       # NOT part of spec
author: "Me"           # NOT part of spec
tags: ["dev", "api"]   # NOT part of spec
---
```

**Critical**: Only `name` and `description` are used by Claude. Additional fields are ignored.

---

### 📂 Directory Structure

#### Minimal Skill (Required)
```
~/.claude/skills/                    # Personal skills location
└── my-skill/                        # Skill directory (MUST be at top level!)
    └── SKILL.md                     # REQUIRED: Main skill file
```

**IMPORTANT**: Skills MUST be directly under `~/.claude/skills/[skill-name]/`.
Claude Code does NOT support nested subdirectories or namespaces!

#### Full-Featured Skill (Recommended)
```
~/.claude/skills/
└── my-skill/                        # Top-level skill directory
        ├── SKILL.md                 # REQUIRED: Main skill file
        ├── README.md                # Optional: Human-readable docs
        ├── scripts/                 # Optional: Executable scripts
        │   ├── setup.sh
        │   ├── validate.js
        │   └── deploy.py
        ├── resources/               # Optional: Supporting files
        │   ├── templates/
        │   │   ├── api-template.js
        │   │   └── component.tsx
        │   ├── examples/
        │   │   └── sample-output.json
        │   └── schemas/
        │       └── config-schema.json
        └── docs/                    # Optional: Additional documentation
            ├── ADVANCED.md
            ├── TROUBLESHOOTING.md
            └── API_REFERENCE.md
```

#### Skills Locations

**Personal Skills** (available across all projects):
```
~/.claude/skills/
└── [your-skills]/
```
- **Path**: `~/.claude/skills/` or `$HOME/.claude/skills/`
- **Scope**: Available in all projects for this user
- **Version Control**: NOT committed to git (outside repo)
- **Use Case**: Personal productivity tools, custom workflows

**Project Skills** (team-shared, version controlled):
```
<project-root>/.claude/skills/
└── [team-skills]/
```
- **Path**: `.claude/skills/` in project root
- **Scope**: Available only in this project
- **Version Control**: SHOULD be committed to git
- **Use Case**: Team workflows, project-specific tools, shared knowledge

---

### 🎯 Progressive Disclosure Architecture

Claude Code uses a **3-level progressive disclosure system** to scale to 100+ skills without context penalty:

#### Level 1: Metadata (Name + Description)
**Loaded**: At Claude Code startup, always
**Size**: ~200 chars per skill
**Purpose**: Enable autonomous skill matching
**Context**: Loaded into system prompt for ALL skills

```yaml
---
name: "API Builder"                   # 11 chars
description: "Creates REST APIs..."   # ~50 chars
---
# Total: ~61 chars per skill
# 100 skills = ~6KB context (minimal!)
```

#### Level 2: SKILL.md Body
**Loaded**: When skill is triggered/matched
**Size**: ~1-10KB typically
**Purpose**: Main instructions and procedures
**Context**: Only loaded for ACTIVE skills

```markdown
# API Builder

## What This Skill Does
[Main instructions - loaded only when skill is active]

## Quick Start
[Basic procedures]

## Step-by-Step Guide
[Detailed instructions]
```

#### Level 3+: Referenced Files
**Loaded**: On-demand as Claude navigates
**Size**: Variable (KB to MB)
**Purpose**: Deep reference, examples, schemas
**Context**: Loaded only when Claude accesses specific files

```markdown
# In SKILL.md
See [Advanced Configuration](docs/ADVANCED.md) for complex scenarios.
See [API Reference](docs/API_REFERENCE.md) for complete documentation.
Use template: `resources/templates/api-template.js`

# Claude will load these files ONLY if needed
```

**Benefit**: Install 100+ skills with ~6KB context. Only active skill content (1-10KB) enters context.

---

### 📝 SKILL.md Content Structure

#### Recommended 4-Level Structure

```markdown
---
name: "Your Skill Name"
description: "What it does and when to use it"
---

# Your Skill Name

## Level 1: Overview (Always Read First)
Brief 2-3 sentence description of the skill.

## Prerequisites
- Requirement 1
- Requirement 2

## What This Skill Does
1. Primary function
2. Secondary function
3. Key benefit

---

## Level 2: Quick Start (For Fast Onboarding)

### Basic Usage
```bash
# Simplest use case
command --option value
```

### Common Scenarios
1. **Scenario 1**: How to...
2. **Scenario 2**: How to...

---

## Level 3: Detailed Instructions (For Deep Work)

### Step-by-Step Guide

#### Step 1: Initial Setup
```bash
# Commands
```
Expected output:
```
Success message
```

#### Step 2: Configuration
- Configuration option 1
- Configuration option 2

#### Step 3: Execution
- Run the main command
- Verify results

### Advanced Options

#### Option 1: Custom Configuration
```bash
# Advanced usage
```

#### Option 2: Integration
```bash
# Integration steps
```

---

## Level 4: Reference (Rarely Needed)

### Troubleshooting

#### Issue: Common Problem
**Symptoms**: What you see
**Cause**: Why it happens
**Solution**: How to fix
```bash
# Fix command
```

#### Issue: Another Problem
**Solution**: Steps to resolve

### Complete API Reference
See [API_REFERENCE.md](docs/API_REFERENCE.md)

### Examples
See [examples/](resources/examples/)

### Related Skills
- [Related Skill 1](#)
- [Related Skill 2](#)

### Resources
- [External Link 1](https://example.com)
- [Documentation](https://docs.example.com)
```

---

### 🎨 Content Best Practices

#### Writing Effective Descriptions

**Front-Load Keywords**:
```yaml
# ✅ GOOD: Keywords first
description: "Generate TypeScript interfaces from JSON schema. Use when converting schemas, creating types, or building API clients."

# ❌ BAD: Keywords buried
description: "This skill helps developers who need to work with JSON schemas by providing a way to generate TypeScript interfaces."
```

**Include Trigger Conditions**:
```yaml
# ✅ GOOD: Clear "when" clause
description: "Debug React performance issues using Chrome DevTools. Use when components re-render unnecessarily, investigating slow updates, or optimizing bundle size."

# ❌ BAD: No trigger conditions
description: "Helps with React performance debugging."
```

**Be Specific**:
```yaml
# ✅ GOOD: Specific technologies
description: "Create Express.js REST endpoints with Joi validation, Swagger docs, and Jest tests. Use when building new APIs or adding endpoints."

# ❌ BAD: Too generic
description: "Build API endpoints with proper validation and testing."
```

#### Progressive Disclosure Writing

**Keep Level 1 Brief** (Overview):
```markdown
## What This Skill Does
Creates production-ready React components with TypeScript, hooks, and tests in 3 steps.
```

**Level 2 for Common Paths** (Quick Start):
```markdown
## Quick Start
```bash
# Most common use case (80% of users)
generate-component MyComponent
```
```

**Level 3 for Details** (Step-by-Step):
```markdown
## Step-by-Step Guide

### Creating a Basic Component
1. Run generator
2. Choose template
3. Customize options
[Detailed explanations]
```

**Level 4 for Edge Cases** (Reference):
```markdown
## Advanced Configuration
For complex scenarios like HOCs, render props, or custom hooks, see [ADVANCED.md](docs/ADVANCED.md).
```

---

### 🛠️ Adding Scripts and Resources

#### Scripts Directory

**Purpose**: Executable scripts that Claude can run
**Location**: `scripts/` in skill directory
**Usage**: Referenced from SKILL.md

Example:
```bash
# In skill directory
scripts/
├── setup.sh          # Initialization script
├── validate.js       # Validation logic
├── generate.py       # Code generation
└── deploy.sh         # Deployment script
```

Reference from SKILL.md:
```markdown
## Setup
Run the setup script:
```bash
./scripts/setup.sh
```

## Validation
Validate your configuration:
```bash
node scripts/validate.js config.json
```
```

#### Resources Directory

**Purpose**: Templates, examples, schemas, static files
**Location**: `resources/` in skill directory
**Usage**: Referenced or copied by scripts

Example:
```bash
resources/
├── templates/
│   ├── component.tsx.template
│   ├── test.spec.ts.template
│   └── story.stories.tsx.template
├── examples/
│   ├── basic-example/
│   ├── advanced-example/
│   └── integration-example/
└── schemas/
    ├── config.schema.json
    └── output.schema.json
```

Reference from SKILL.md:
```markdown
## Templates
Use the component template:
```bash
cp resources/templates/component.tsx.template src/components/MyComponent.tsx
```

## Examples
See working examples in `resources/examples/`:
- `basic-example/` - Simple component
- `advanced-example/` - With hooks and context
```

---

### 🔗 File References and Navigation

Claude can navigate to referenced files automatically. Use these patterns:

#### Markdown Links
```markdown
See [Advanced Configuration](docs/ADVANCED.md) for complex scenarios.
See [Troubleshooting Guide](docs/TROUBLESHOOTING.md) if you encounter errors.
```

#### Relative File Paths
```markdown
Use the template located at `resources/templates/api-template.js`
See examples in `resources/examples/basic-usage/`
```

#### Inline File Content
```markdown
## Example Configuration
See `resources/examples/config.json`:
```json
{
  "option": "value"
}
```
```

**Best Practice**: Keep SKILL.md lean (~2-5KB). Move lengthy content to separate files and reference them. Claude will load only what's needed.

---

### ✅ Validation Checklist

Before publishing a skill, verify:

**YAML Frontmatter**:
- [ ] Starts with `---`
- [ ] Contains `name` field (max 64 chars)
- [ ] Contains `description` field (max 1024 chars)
- [ ] Description includes "what" and "when"
- [ ] Ends with `---`
- [ ] No YAML syntax errors

**File Structure**:
- [ ] SKILL.md exists in skill directory
- [ ] Directory is DIRECTLY in `~/.claude/skills/[skill-name]/` or `.claude/skills/[skill-name]/`
- [ ] Uses clear, descriptive directory name
- [ ] **NO nested subdirectories** (Claude Code requires top-level structure)

**Content Quality**:
- [ ] Level 1 (Overview) is brief and clear
- [ ] Level 2 (Quick Start) shows common use case
- [ ] Level 3 (Details) provides step-by-step guide
- [ ] Level 4 (Reference) links to advanced content
- [ ] Examples are concrete and runnable
- [ ] Troubleshooting section addresses common issues

**Progressive Disclosure**:
- [ ] Core instructions in SKILL.md (~2-5KB)
- [ ] Advanced content in separate docs/
- [ ] Large resources in resources/ directory
- [ ] Clear navigation between levels

**Testing**:
- [ ] Skill appears in Claude's skill list
- [ ] Description triggers on relevant queries
- [ ] Instructions are clear and actionable
- [ ] Scripts execute successfully (if included)
- [ ] Examples work as documented

---

## Skill Builder Templates

### Template 1: Basic Skill (Minimal)

```markdown
---
name: "My Basic Skill"
description: "One sentence what. One sentence when to use."
---

# My Basic Skill

## What This Skill Does
[2-3 sentences describing functionality]

## Quick Start
```bash
# Single command to get started
```

## Step-by-Step Guide

### Step 1: Setup
[Instructions]

### Step 2: Usage
[Instructions]

### Step 3: Verify
[Instructions]

## Troubleshooting
- **Issue**: Problem description
  - **Solution**: Fix description
```

### Template 2: Intermediate Skill (With Scripts)

```markdown
---
name: "My Intermediate Skill"
description: "Detailed what with key features. When to use with specific triggers: scaffolding, generating, building."
---

# My Intermediate Skill

## Prerequisites
- Requirement 1
- Requirement 2

## What This Skill Does
1. Primary function
2. Secondary function
3. Integration capability

## Quick Start
```bash
./scripts/setup.sh
./scripts/generate.sh my-project
```

## Configuration
Edit `config.json`:
```json
{
  "option1": "value1",
  "option2": "value2"
}
```

## Step-by-Step Guide

### Basic Usage
[Steps for 80% use case]

### Advanced Usage
[Steps for complex scenarios]

## Available Scripts
- `scripts/setup.sh` - Initial setup
- `scripts/generate.sh` - Code generation
- `scripts/validate.sh` - Validation

## Resources
- Templates: `resources/templates/`
- Examples: `resources/examples/`

## Troubleshooting
[Common issues and solutions]
```

### Template 3: Advanced Skill (Full-Featured)

```markdown
---
name: "My Advanced Skill"
description: "Comprehensive what with all features and integrations. Use when [trigger 1], [trigger 2], or [trigger 3]. Supports [technology stack]."
---

# My Advanced Skill

## Overview
[Brief 2-3 sentence description]

## Prerequisites
- Technology 1 (version X+)
- Technology 2 (version Y+)
- API keys or credentials

## What This Skill Does
1. **Core Feature**: Description
2. **Integration**: Description
3. **Automation**: Description

---

## Quick Start (60 seconds)

### Installation
```bash
./scripts/install.sh
```

### First Use
```bash
./scripts/quickstart.sh
```

Expected output:
```
✓ Setup complete
✓ Configuration validated
→ Ready to use
```

---

## Configuration

### Basic Configuration
Edit `config.json`:
```json
{
  "mode": "production",
  "features": ["feature1", "feature2"]
}
```

### Advanced Configuration
See [Configuration Guide](docs/CONFIGURATION.md)

---

## Step-by-Step Guide

### 1. Initial Setup
[Detailed steps]

### 2. Core Workflow
[Main procedures]

### 3. Integration
[Integration steps]

---

## Advanced Features

### Feature 1: Custom Templates
```bash
./scripts/generate.sh --template custom
```

### Feature 2: Batch Processing
```bash
./scripts/batch.sh --input data.json
```

### Feature 3: CI/CD Integration
See [CI/CD Guide](docs/CICD.md)

---

## Scripts Reference

| Script | Purpose | Usage |
|--------|---------|-------|
| `install.sh` | Install dependencies | `./scripts/install.sh` |
| `generate.sh` | Generate code | `./scripts/generate.sh [name]` |
| `validate.sh` | Validate output | `./scripts/validate.sh` |
| `deploy.sh` | Deploy to environment | `./scripts/deploy.sh [env]` |

---

## Resources

### Templates
- `resources/templates/basic.template` - Basic template
- `resources/templates/advanced.template` - Advanced template

### Examples
- `resources/examples/basic/` - Simple example
- `resources/examples/advanced/` - Complex example
- `resources/examples/integration/` - Integration example

### Schemas
- `resources/schemas/config.schema.json` - Configuration schema
- `resources/schemas/output.schema.json` - Output validation

---

## Troubleshooting

### Issue: Installation Failed
**Symptoms**: Error during `install.sh`
**Cause**: Missing dependencies
**Solution**:
```bash
# Install prerequisites
npm install -g required-package
./scripts/install.sh --force
```

### Issue: Validation Errors
**Symptoms**: Validation script fails
**Solution**: See [Troubleshooting Guide](docs/TROUBLESHOOTING.md)

---

## API Reference
Complete API documentation: [API_REFERENCE.md](docs/API_REFERENCE.md)

## Related Skills
- [Related Skill 1](../related-skill-1/)
- [Related Skill 2](../related-skill-2/)

## Resources
- [Official Documentation](https://example.com/docs)
- [GitHub Repository](https://github.com/example/repo)
- [Community Forum](https://forum.example.com)

---

**Created**: 2025-10-19
**Category**: Advanced
**Difficulty**: Intermediate
**Estimated Time**: 15-30 minutes
```

---

## Examples from the Wild

### Example 1: Simple Documentation Skill

```markdown
---
name: "README Generator"
description: "Generate comprehensive README.md files for GitHub repositories. Use when starting new projects, documenting code, or improving existing READMEs."
---

# README Generator

## What This Skill Does
Creates well-structured README.md files with badges, installation, usage, and contribution sections.

## Quick Start
```bash
# Answer a few questions
./scripts/generate-readme.sh

# README.md created with:
# - Project title and description
# - Installation instructions
# - Usage examples
# - Contribution guidelines
```

## Customization
Edit sections in `resources/templates/sections/` before generating.
```

### Example 2: Code Generation Skill

```markdown
---
name: "React Component Generator"
description: "Generate React functional components with TypeScript, hooks, tests, and Storybook stories. Use when creating new components, scaffolding UI, or following component architecture patterns."
---

# React Component Generator

## Prerequisites
- Node.js 18+
- React 18+
- TypeScript 5+

## Quick Start
```bash
./scripts/generate-component.sh MyComponent

# Creates:
# - src/components/MyComponent/MyComponent.tsx
# - src/components/MyComponent/MyComponent.test.tsx
# - src/components/MyComponent/MyComponent.stories.tsx
# - src/components/MyComponent/index.ts
```

## Step-by-Step Guide

### 1. Run Generator
```bash
./scripts/generate-component.sh ComponentName
```

### 2. Choose Template
- Basic: Simple functional component
- With State: useState hooks
- With Context: useContext integration
- With API: Data fetching component

### 3. Customize
Edit generated files in `src/components/ComponentName/`

## Templates
See `resources/templates/` for available component templates.
```

---

## Learn More

### Official Resources
- [Anthropic Agent Skills Documentation](https://docs.claude.com/en/docs/agents-and-tools/agent-skills)
- [GitHub Skills Repository](https://github.com/anthropics/skills)
- [Claude Code Documentation](https://docs.claude.com/en/docs/claude-code)

### Community
- [Skills Marketplace](https://github.com/anthropics/skills) - Browse community skills
- [Anthropic Discord](https://discord.gg/anthropic) - Get help from community

### Advanced Topics
- Multi-file skills with complex navigation
- Skills that spawn other skills
- Integration with MCP tools
- Dynamic skill generation

---

**Created**: 2025-10-19
**Version**: 1.0.0
**Maintained By**: agentic-flow team
**License**: MIT