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

1. •Discovery — Understand what the skill should do
2. •Archetype Selection — Choose the best pattern
3. •Initialization — Create skill structure
4. •Customization — Tailor to specific needs
5. •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

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]
---

Important:

• •Always wrap description in double quotes — values containing colons, commas, or special characters can break YAML parsing otherwise.
• •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 document extraction."

Checklist:

• • Explains WHAT (capabilities)
• • States WHEN (trigger conditions)
• • Includes 3-5 trigger KEYWORDS
• • Uses third-person voice
• • Under 200 words

Stage 5: Validation

Validation Checklist

A. YAML Frontmatter

• • Opens with --- on line 1, closes with ---
• • name and description present (required)
• • description wrapped in double quotes
• • 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:

1. •Metadata (~100 tokens): name + description at startup
2. •Instructions (<5000 tokens): SKILL.md body when activated
3. •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

External Resources

• •Agent Skills Specification
• •Best Practices Guide
• •skills-ref Validation Library