What is a Claude Skill?

A factual guide to Anthropic's extensibility format

SKILL GUIDE

Definition

A Claude Skill is a portable instruction package that teaches Claude how to do a specific task. The format was introduced by Anthropic to let users extend Claude Code, Claude Desktop, and Claude.ai with reusable capabilities. A skill typically contains prompt instructions that guide Claude's behavior, plus optional code helpers—Python or Node.js libraries—that perform concrete operations like generating files, calling APIs, or manipulating data. Skills install to the ~/.claude/skills/ directory and are discovered automatically by Claude Code when it starts.

How it works

When Claude Code loads, it scans ~/.claude/skills/ for subdirectories containing skill definitions. Each skill directory includes a prompt file that tells Claude when and how to use the skill, what parameters it accepts, and what outputs it produces. The prompt acts as a contract between the user and Claude: it defines the task boundary and expected behavior.

Some skills are prompt-only. These work entirely within Claude's context window and require no external dependencies. Other skills bundle executable code. For example, a PowerPoint generation skill might include Python scripts that use python-pptx or Node scripts that use pptxgenjs to construct .pptx files from structured data. When Claude decides to use such a skill, it runs the associated code in the user's environment, passing parameters extracted from the conversation.

The skill system is explicit: Claude does not silently invoke skills. It evaluates whether a user's request matches a loaded skill's described purpose, then either uses the skill or proceeds with its base capabilities. This design keeps the user in control and makes skill behavior inspectable.

Examples on powerpoint.md

The powerpoint.md directory catalogs skills for presentation and document generation. Below are five entries you can install today:

Anthropic PPTX Skill

Official Anthropic skill • Output: PPTX • Install: heavy • No API key

MiniMax PPTX Generator

Community skill • Output: PPTX • Install: heavy • No API key

Polished Documents (10 Brand Themes)

Community skill • Output: DOCX • Install: pip • No API key

PPTAgent v2

Community skill • Output: PPTX • Install: heavy • Requires OpenAI API key

Frontend Slides

Community skill • Output: HTML • Install: pip • No API key

Frequently asked questions

What is a Claude Skill?

A Claude Skill is a portable instruction package that teaches Claude (Code, Desktop, or .ai) how to do a specific task. Skills bundle prompts with optional code helpers and install to ~/.claude/skills/.

How do I install a Claude Skill?

Most skills install by cloning a Git repository and copying a directory to ~/.claude/skills/. Some require additional steps like installing Python packages with pip or Node packages with npm. Each skill's page on powerpoint.md provides its exact install command.

Do Claude Skills work with all Claude products?

Skills are designed for Claude Code, Claude Desktop, and Claude.ai. Availability varies by product. Claude Code has the most direct skill integration via the ~/.claude/skills/ directory.

Do Claude Skills require API keys?

Most skills do not require API keys. Some advanced skills like PPTAgent v2 require an OpenAI API key for certain features. The powerpoint.md directory labels each skill's API key requirements.

What kinds of tasks can Claude Skills do?

Skills cover document generation (PowerPoint, Word, HTML slides), code refactoring, data analysis, and more. The powerpoint.md directory focuses on presentation and document skills.