skills-reference

# Claude Code Skills Reference

Skills extend Claude's capabilities. They're defined as Markdown files that Claude loads when needed.

## Two Types of Skills

| Type | Trigger | Use Case |
|------|---------|----------|
| **Model-invoked** | Claude decides automatically | Reference docs, specialized knowledge |
| **User-invoked** | User types `/skill-name` | Workflows, actions with side effects |

## Skill File Structure

```
~/.claude/skills/           # User skills (all projects)
.claude/skills/             # Project skills (team shared)

skill-name/
├── SKILL.md               # Required: skill definition
├── reference.md           # Optional: additional docs
└── scripts/               # Optional: supporting files
```

## SKILL.md Format

```markdown
---
name: my-skill
description: What this skill does and when Claude should use it
user_invocable: false
model: sonnet
tools:
  - Read
  - Bash
---

# Skill Title

Instructions Claude follows when this skill is activated.

## When to Use

Describe scenarios when this skill applies.

## How to Execute

Step-by-step instructions for Claude.
```

## Frontmatter Fields

| Field | Required | Type | Description |
|-------|----------|------|-------------|
| `name` | Yes | string | Skill identifier |
| `description` | Yes | string | When/why to use this skill |
| `user_invocable` | No | boolean | Allow `/skill-name` invocation |
| `model` | No | string | Model to use (haiku, sonnet, opus) |
| `tools` | No | array | Restrict available tools |
| `allowed_tools` | No | array | Alias for `tools` |

## Model-Invoked Skills

Claude automatically uses these when the task matches the description.

```markdown
---
name: python-debugging
description: Debug Python code. Use when user encounters Python errors, exceptions, or unexpected behavior.
---

# Python Debugging

When debugging Python code:
1. Read the error traceback carefully
2. Identify the failing line and function
3. Check variable types and values
...
```

## User-Invoked Ski