Creating Agent Skills

Agent Skills extend Claude's capabilities with specialized knowledge and workflows. This skill helps you create effective skills that follow best practices.

Use this skill when creating new skills, improving existing ones, or designing skill architecture for projects.

Supporting files: SPECIFICATION.md for format details, BEST-PRACTICES.md for authoring guidelines, TEMPLATES.md for starter templates.

Quick Start

Create a skill directory with SKILL.md:

my-skill/
├── SKILL.md          # Required: metadata + instructions
├── scripts/          # Optional: executable code
├── references/       # Optional: detailed docs
└── assets/           # Optional: templates, resources

SKILL.md Structure

---
name: skill-name          # lowercase, hyphens only, max 64 chars
description: What it does and when to use it.  # max 1024 chars
---

# Skill Title

Brief intro and "Use this skill when..." statement.

## Quick Start
[Most common use case with example]

## Core Features
[Main capabilities organized by task]

## Support Files
[Links to reference files for detailed info]

Naming Conventions

Use gerund form (verb + -ing) for clarity:

• processing-pdfs (preferred)
• analyzing-data (preferred)
• pdf-processor (acceptable)

Rules:

• Lowercase letters, numbers, hyphens only
• No consecutive hyphens (--)
• Cannot start/end with hyphen
• Max 64 characters

Writing Descriptions

Descriptions drive skill discovery. Include:

1. What it does (actions/capabilities)
2. When to use it (triggers/contexts)

Good:

description: Extracts text and tables from PDF files, fills forms, merges documents. Use when working with PDF files or when user mentions PDFs, forms, or document extraction.

Bad:

description: Helps with PDFs.  # Too vague

Always use third person (description is injected into system prompt).

Progressive Disclosure

Keep SKILL.md under 500 lines. Split content strategically:

1. Metadata (~100 tokens): Loaded at startup for all skills
2. SKILL.md body (<5000 tokens): Loaded when skill activates
3. Reference files: Loaded only when needed

## Detailed Topics

**Form filling**: See [FORMS.md](references/FORMS.md)
**API reference**: See [REFERENCE.md](references/REFERENCE.md)
**Examples**: See [EXAMPLES.md](references/EXAMPLES.md)

Key Principles

1. Be concise: Claude is smart; only add context it doesn't have
2. Test with all models: What works for Opus may need detail for Haiku
3. Use workflows: Break complex tasks into clear, sequential steps
4. Include feedback loops: Validate → fix → repeat for quality
5. Avoid time-sensitive info: Use "old patterns" sections instead

Checklist

Before finalizing a skill:

• Name uses lowercase/hyphens, matches directory name
• Description explains what AND when
• SKILL.md under 500 lines
• Reference files for detailed content
• Examples are concrete, not abstract
• Tested with real usage scenarios

Resources

• Agent Skills Specification
• Best Practices
• Example Skills