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:

• 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)

• 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

External Resources

• Agent Skills Specification

• Best Practices Guide

• skills-ref Validation Library