Skill Builder

# 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