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Claude Skills (also referred to as Agent Skills) are modular capabilities developed by Anthropic for the Claude platform that package repeatable workflows, instructions, reference materials, and optional executable scripts into discoverable components that Claude can automatically load when relevant to a task.[1] Introduced on October 16, 2025, Skills transform Claude from a general-purpose AI assistant into a specialized agent for specific workflows while maintaining efficiency through progressive disclosure of context.[2]
Skills work across Claude apps, Claude Code, and the Claude Developer Platform (API), enabling users to create consistent, specialized behaviors without prompt overhead. Anthropic also publishes a public repository of example skills and the engineering design pattern underpinning the Skills system.[3]
A Skill is a directory-based package that contains:
SKILL.md file with YAML frontmatter (name and description) and Markdown instructionsClaude uses a progressive disclosure mechanism to manage Skills efficiently: it preloads only lightweight metadata (name and description) for all installed skills at session start; when a user request suggests a skill is relevant, Claude reads the full SKILL.md and any linked files; if appropriate, it may execute bundled scripts within its code execution environment.[4]
The core design principle behind Claude Skills is progressive disclosure, which operates on three levels:[2]
| Level | Content | Token Usage | When Loaded |
|---|---|---|---|
| 1. Metadata | Name and description from YAML frontmatter | ~30-50 tokens per skill | At session start |
| 2. Core Instructions | Full SKILL.md file content | Variable (hundreds to thousands) | When skill is triggered |
| 3. Additional Resources | Referenced files, scripts, templates | As needed | Only when specifically required |
This architecture ensures that Claude's context window remains efficient, as skills that aren't relevant to the current task don't consume tokens beyond their minimal metadata.[5]
A minimal SKILL.md uses YAML frontmatter and Markdown content:[6]
--- name: pdf-processing description: Extract text, fill forms, and merge PDFs. Use when working with PDF files or forms. version: 1.0.0 --- # PDF Processing ## Instructions [Detailed instructions for the skill] ## Examples [Usage examples]
| Characteristic | Description |
|---|---|
| Composable | Multiple skills can stack and work together seamlessly; Claude autonomously identifies and coordinates the set of relevant skills.[1] |
| Portable | The same skill format works across Claude apps, Claude Code, and the API—"build once, use everywhere."[1] |
| Efficient | Progressive disclosure keeps context use minimal until needed; reduces prompt bloat and token consumption.[2] |
| Powerful | Skills may include executable code for deterministic operations (for example PDF form extraction) inside Claude's sandboxed container.[2] |
| Secure | Skills operate in isolated environments with no data persistence between sessions.[7] |
Skills were announced publicly on October 16, 2025. Availability varies by platform:[1]
| Platform | Availability | Requirements |
|---|---|---|
| Claude.ai apps | Pro, Max, Team, Enterprise plans | Code execution and file creation enabled |
| Claude Code | All users with Claude Code access | Installed via plugins or filesystem |
| Claude API | All API users | Code Execution Tool beta enabled |
| Claude Agent SDK | All SDK users | Standard SDK requirements |
For Team and Enterprise users, administrators must first enable Skills organization-wide before individual members can use them.[7]
Anthropic provides built-in document Skills that Claude can invoke automatically when appropriate:[7]
| skill_id | Capability | Description |
|---|---|---|
docx |
Word documents | Creates, edits, and analyzes Microsoft Word documents with support for tracked changes, comments, and formatting preservation |
xlsx |
Excel spreadsheets | Generates Microsoft Excel spreadsheets with formulas, data analysis, and visualization capabilities |
pptx |
PowerPoint presentations | Creates Microsoft PowerPoint presentations with layouts, templates, and automated slide generation |
pdf |
PDF manipulation | Comprehensive PDF handling including form filling, text extraction, merging, and splitting |
Anthropic's GitHub repository includes diverse example Skills:[3]
| Category | Skill Name | Description |
|---|---|---|
| Creative & Design | algorithmic-art | Generates art using p5.js with seeded randomness and particle systems |
| canvas-design | Creates visual art in PNG and PDF formats using design philosophies | |
| slack-gif-creator | Produces animated GIFs optimized for Slack's size constraints | |
| Development & Technical | artifacts-builder | Builds HTML artifacts using React and Tailwind CSS |
| mcp-server | Guides creation of MCP servers for API integration | |
| webapp-testing | Tests web applications using Playwright | |
| Enterprise & Communication | brand-guidelines | Applies brand colors, typography, and organizational standards |
| internal-comms | Writes internal communications like reports and newsletters | |
| theme-factory | Styles artifacts with professional themes | |
| Meta Skills | skill-creator | Interactive guidance for creating new Skills |
| template-skill | Basic template for starting new Skills |
Skills operate within Claude's sandboxed code execution environment, which provides:[8]
The Code Execution Tool beta must be enabled for Skills to function.[1]
The API supports both Anthropic-managed and custom Skills through:[9]
| Requirement | Details |
|---|---|
| Beta headers | code-execution-2025-08-25, skills-2025-10-02, files-api-2025-04-14
|
| Endpoints | /v1/skills for management; Messages API for execution
|
| Skill specification | List in container.skills with type, skill_id, and optional version
|
| File outputs | Generated files include file_id for download via Files API
|
| Per-request limit | Maximum 8 Skills per request |
| Upload size limit | Under 8 MB for custom skills |
Example API usage:
{ "container": { "skills": [ {"type": "anthropic", "skill_id": "xlsx", "version": "1.0.0"}, {"type": "custom", "skill_id": "brand-guidelines", "version": "latest"} ] } }
In Claude Code, Skills are discovered from:[6]
~/.claude/skills/.claude/skills/ (in the repository)There are two primary paths for creating custom Skills:[10]
1. Create a folder with the skill name (lowercase, hyphens, max 64 characters)
2. Add SKILL.md with YAML frontmatter and Markdown instructions
3. Include optional scripts, templates, or reference files
4. Upload as ZIP file (Claude apps) or place in appropriate directory (Claude Code/API)
1. Enable the built-in skill-creator Skill in Settings 2. Describe the desired workflow to Claude 3. Claude generates properly structured Skill folder 4. Test and iterate on the generated skill[11]
Several major organizations have implemented Claude Skills for production workflows:
Rakuten, the Japanese e-commerce giant, uses Skills to transform finance operations. According to Yusuke Kaji, General Manager of AI at Rakuten: "Skills streamline our management accounting and finance workflows. Claude processes multiple spreadsheets, catches critical anomalies, and generates reports using our procedures. What once took a day, we can now accomplish in an hour."[12]
Box leverages Skills to make corporate content repositories more actionable. Yashodha Bhavnani, Head of AI at Box, stated: "Skills teaches Claude how to work with Box content. Users can transform stored files into PowerPoint presentations, Excel spreadsheets, and Word documents that follow their organization's standards—saving hours of effort."[1]
Notion integrated Skills to provide more predictable results and reduce prompt complexity. The company reports that Skills enable Claude to work seamlessly with Notion, taking users "from questions to action faster" with "less prompt wrangling on complex tasks."[1]
Canva uses Skills to streamline design workflows and maintain brand consistency across generated content.[1]
Claude Skills operate within a comprehensive sandboxing system that provides:[13]
Organizations implementing Skills should follow these guidelines:[14]
Custom Skills uploaded in apps are private to the individual account; sharing requires separate uploads or API deployment.[7]
While both Claude Skills and the Model Context Protocol aim to extend AI capabilities, they differ significantly:[15]
| Aspect | Claude Skills | Model Context Protocol |
|---|---|---|
| Architecture | Markdown files with optional scripts | Full protocol specification with servers |
| Token efficiency | 30-50 tokens until loaded | Thousands to tens of thousands |
| Complexity | Simple folder structure | Requires API design knowledge |
| Primary function | Teaching HOW to perform tasks | Connecting TO external systems |
| Portability | Cross-platform by default | Vendor-neutral but complex |
| Use case | Procedural knowledge and workflows | External service integration |
Developer and AI researcher Simon Willison noted that Skills "might be a bigger deal than MCP," citing their simplicity and effectiveness.[16]
Common issues and solutions:[7]
Anthropic has announced plans for several enhancements:[1]
| Date | Milestone | Source |
|---|---|---|
| October 16, 2025 | Public announcement of Agent Skills; availability across Claude apps, Claude Code, and API | [1] |
| October 2025 | Launch of public GitHub repository with example Skills | [3] |
| October 2025 | Integration announced with enterprise partners (Box, Notion, Canva, Rakuten) | [1] |