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

# 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:

---
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

---
# ✅ 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

---
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

# 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

# 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

---
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

# 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

# Advanced usage

Option 2: Integration

# Integration steps

Level 4: Reference (Rarely Needed)

Troubleshooting

Issue: Common Problem

Symptoms: What you see Cause: Why it happens Solution: How to fix

# Fix command

Issue: Another Problem

Solution: Steps to resolve

Complete API Reference

See API_REFERENCE.md

Examples

See examples/

Related Skills

• Related Skill 1
• Related Skill 2

Resources

• External Link 1
• Documentation

---

### 🎨 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:

# ✅ 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:

# ✅ 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):

## What This Skill Does
Creates production-ready React components with TypeScript, hooks, and tests in 3 steps.

Level 2 for Common Paths (Quick Start):

## 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):

## 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:

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

Reference from SKILL.md:

## Setup
Run the setup script:
```bash
./scripts/setup.sh

Validation

Validate your configuration:

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:

## 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

Use the template located at `resources/templates/api-template.js`
See examples in `resources/examples/basic-usage/`

Inline File Content

## 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:

{
  "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-config.json - 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

./scripts/quickstart.sh

Expected output:

✓ Setup complete
✓ Configuration validated
→ Ready to use

Configuration

Basic Configuration

Edit config.json:

{
  "mode": "production",
  "features": ["feature1", "feature2"]
}

Advanced Configuration

See Configuration Guide

Step-by-Step Guide

1. Initial Setup

[Detailed steps]

2. Core Workflow

[Main procedures]

3. Integration

[Integration steps]

Advanced Features

Feature 1: Custom Templates

./scripts/generate.sh --template custom

Feature 2: Batch Processing

./scripts/batch.sh --input data.json

Feature 3: CI/CD Integration

See CI/CD Guide

Scripts Reference

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:

# Install prerequisites
npm install -g required-package
./scripts/install.sh --force

Issue: Validation Errors

Symptoms: Validation script fails Solution: See Troubleshooting Guide

API Reference

Complete API documentation: API_REFERENCE.md

Related Skills

• Related Skill 1
• Related Skill 2

Resources

• Official Documentation
• GitHub Repository
• Community Forum

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

./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