Create Skill

Guide for creating effective skills that extend agent capabilities with specialized knowledge, workflows, and tool integrations.

About Skills

Skills are modular, self-contained packages that extend agent capabilities by providing specialized knowledge, workflows, and tools. Think of them as “onboarding guides” for specific domains or tasks.

What Skills Provide

1. Specialized workflows – Multi-step procedures for specific domains
2. Tool integrations – Instructions for working with specific file formats or APIs
3. Domain expertise – Company-specific knowledge, schemas, business logic
4. Bundled resources – Scripts, references, and assets for complex and repetitive tasks

Progressive Disclosure Principle

The 200-line rule is critical. SKILL.md must be under 200 lines. If you need more, split content into references/ files.

Three-Level Loading System

1. Metadata (name + description) – Always in context (~100 words)
2. SKILL.md body – When skill triggers (<200 lines, ideally <500 lines for optimal performance)
3. Bundled resources – As needed by agent (unlimited)

Why Progressive Disclosure Matters

• 85% reduction in initial context load
• Activation times drop from 500ms+ to under 100ms
• Agent loads only what’s needed, when it’s needed
• Skills remain maintainable and focused

Skill Structure

skill-name/
├── SKILL.md (required, <200 lines)
│   ├── YAML frontmatter metadata (required)
│   │   ├── name: (required)
│   │   └── description: (required)
│   └── Markdown instructions (required)
└── Bundled Resources (optional)
    ├── scripts/          - Executable code
    ├── references/       - Documentation loaded as needed
    └── assets/           - Files used in output

Core Principles

Concise is Key

The context window is a shared resource. Your skill shares it with everything else the agent needs. Be concise and challenge each piece of information:

• Does the agent really need this explanation?
• Can I assume the agent knows this?
• Does this paragraph justify its token cost?

Set Appropriate Degrees of Freedom

• High freedom: Text-based instructions for multiple valid approaches
• Medium freedom: Pseudocode or scripts with parameters
• Low freedom: Specific scripts with few/no parameters for fragile operations

Test with All Models

Skills act as additions to models, so effectiveness depends on the underlying model. Test your skill with all models you plan to use it with.

References

For detailed guidance, see:

• references/progressive-disclosure.md – 200-line rule and references pattern
• references/skill-structure.md – SKILL.md format and frontmatter details
• references/examples.md – Good skill examples
• references/best-practices.md – Comprehensive best practices guide