Skills Development

Create skills that follow the Agent Skills specification—an open format supported by Claude Code, Cursor, VS Code, GitHub Copilot, Codex, and other agent products.

Workflow

Discovery — Understand what the skill should do
Archetype Selection — Choose the best pattern
Initialization — Create skill structure
Customization — Tailor to specific needs
Validation — Verify quality before committing

Stage 1: Discovery

Ask about the skill:

What problem does this skill solve?
What are the main capabilities?
What triggers should invoke it? (phrases users would say)
Where should it live? (personal, project, or plugin)

Stage 2: Archetype Selection

Archetype	Use When	Example
simple	Basic skill without scripts	Quick reference, style guide
api-wrapper	Wrapping external APIs	GitHub API, Stripe API
document-processor	Working with file formats	PDF extractor, Excel analyzer
dev-workflow	Automating development tasks	Git workflow, project scaffolder
research-synthesizer	Gathering and synthesizing information	Competitive analysis, literature review

Stage 3: Directory Structure

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

Stage 4: Frontmatter Schema

---
name: skill-name
description: What it does and when to use it. Include trigger keywords.
version: 1.0.0                         # optional, recommended
license: Apache-2.0                    # optional
compatibility: Requires git and jq     # optional
metadata:                              # optional
  author: your-org
  category: development
  tags: [testing, automation]
---

Field	Required	Constraints
`name`	Yes	2-64 chars, lowercase/numbers/hyphens, must match directory
`description`	Yes	10-1024 chars, describes what + when
`version`	No	Semantic version (MAJOR.MINOR.PATCH)
`license`	No	License name or reference
`compatibility`	No	1-500 chars, environment requirements
`metadata`	No	Object for custom fields

Note: Platform-specific fields (e.g., Claude's allowed-tools, user-invocable) should be added per-platform. See claude-code.md for Claude Code extensions.

Custom Frontmatter

Custom fields must be nested under metadata:

---
name: my-skill
description: ...
metadata:
  author: your-org
  version: "1.0"
  category: development
  tags: [typescript, testing]
---

Top-level custom fields are not allowed and may cause parsing errors.

Description Formula

[WHAT] + [WHEN] + [TRIGGERS]

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

Checklist:

Stage 5: Validation

Validation Checklist

A. YAML Frontmatter

Opens with --- on line 1, closes with ---
name and description present (required)
Uses spaces, not tabs
Special characters quoted

B. Naming

Lowercase, numbers, hyphens only (1-64 chars)
Matches parent directory name
No --, leading/trailing hyphens
No anthropic or claude in name

C. Description Quality

WHAT: Explains capabilities
WHEN: States "Use when..." conditions
TRIGGERS: 3-5 keywords users would say
Third-person voice (not "I can" or "you can")

D. Structure

SKILL.md under 500 lines
All referenced files exist
No TODO/placeholder markers
Progressive disclosure (details in references/)

Report Format

# Skill Check: {skill-name}

**Status**: PASS | WARNINGS | FAIL
**Issues**: {critical} critical, {warnings} warnings

## Critical (must fix)
1. {issue with fix}

## Warnings (should fix)
1. {issue with fix}

## Strengths
- {what's done well}

Core Principles

Concise is key

Context window is shared. Only include what the agent doesn't already know. Challenge each paragraph—does it justify its token cost?

Third-person descriptions

Descriptions inject into system prompt:

"Extracts text from PDFs"
"I can help you extract text from PDFs"

Progressive disclosure

Keep SKILL.md under 500 lines. Move details to:

references/ - Detailed docs, API references
scripts/ - Executable utilities (code never enters context)
assets/ - Templates, data files

Token loading:

Metadata (~100 tokens): name + description at startup
Instructions (<5000 tokens): SKILL.md body when activated
Resources (as needed): files loaded only when referenced

Degrees of freedom

Match instruction specificity to task requirements:

High freedom (text): Multiple valid approaches, use judgment
Medium freedom (pseudocode): Preferred pattern with variation allowed
Low freedom (scripts): Exact sequence required, no deviation

See patterns.md for detailed examples.

Naming Requirements

Lowercase letters, numbers, hyphens only
Cannot start/end with hyphen or contain --
Must match parent directory name
Cannot contain anthropic or claude

Recommended: Gerund form (processing-pdfs, reviewing-code)

Platform-Specific Guidance

Skills are cross-platform, but each tool has specific implementation details:

Claude Code: See claude-code.md for tool restrictions, testing, troubleshooting, and Claude-specific frontmatter extensions
Codex CLI: See codex.md for discovery paths, $skill-name invocation

See implementations.md for storage paths and invocations.md for activation patterns.

References

steps-pattern.md - Composable skill workflows with dependencies
patterns.md - Degrees of freedom, script design, variant organization
best-practices.md - Community patterns, testing strategies
quick-reference.md - Fast checklist and one-liners
implementations.md - Per-tool storage paths
invocations.md - How tools activate skills
compatibility.md - Path compatibility matrix

skills-dev