Write Once, Run Anywhere.
The universal standard for building, validating, and packaging AI Agent Skills.
Toolkit for authoring and packaging Agent Skills. Includes a meta skill, templates, a sample skill, and scripts for validation and packaging.
Every skill consists of a required SKILL.md file and optional bundled resources:
skill-name/
├── SKILL.md (required)
│ ├── YAML frontmatter (required)
│ │ ├── name: (required)
│ │ └── description: (required)
│ └── Markdown instructions (required)
└── Bundled Resources (optional)
├── scripts/ - Executable code (Python/Bash/etc.)
├── references/ - Documentation intended to be loaded into context as needed
└── assets/ - Files used in output (templates, icons, fonts, etc.)- Update owner metadata in .claude-plugin/marketplace.json.
- Use skill-creator or run the toolkit scripts to create new skills.
- Validate and package skills for distribution.
| Script | Purpose | Command |
|---|---|---|
scripts/init_skill.py |
Scaffold a new skill directory with starter resources | python scripts/init_skill.py my-new-skill --path skills |
scripts/validate_skill.py |
Validate SKILL.md frontmatter and structure |
python scripts/validate_skill.py skills/my-new-skill |
scripts/package_skill.py |
Validate and package a skill as a zip archive | python scripts/package_skill.py skills/my-new-skill |
The initializer creates example files in scripts/, references/, and assets/ so you can customize or delete them.
This kit works in VS Code, Cursor, Antigravity, Claude CLI/Web, and other IDEs because skills are plain Markdown folders.
| IDE / Platform | Default Skill Location | Quick Setup | Docs |
|---|---|---|---|
| VS Code (GitHub Copilot) | .github/skills |
Set chat.agentSkillsLocations to include ./skills, or symlink skills → .github/skills |
https://code.visualstudio.com/docs/copilot/customization/agent-skills |
| Cursor | .cursor/skills or .claude/skills |
Symlink skills → .cursor/skills, or import as remote GitHub rule |
https://cursor.com/docs/context/skills |
| Google Antigravity | .agent/skills |
Create .agent/skills and link/copy the repository skills/ folder |
https://antigravity.google/docs/skills |
| Claude (CLI & Web) | .claude/skills (project or global) |
Add plugin source with /plugin marketplace add ... or manually copy skill folders |
https://platform.claude.com/docs/en/agents-and-tools/agent-skills/overview |
| Platform | macOS / Linux | Windows |
|---|---|---|
| Cursor | ln -s skills .cursor/skills |
mklink /D .cursor\skills skills |
| Antigravity | mkdir -p .agent && ln -s ../skills .agent/skills |
mkdir .agent + mklink /D .agent\skills ..\skills |
For Claude CLI plugin registration:
/plugin marketplace add https://github.com/bcastelino/agent-skills-kit.git
Use the skill-creator or start from templates:
skills/skill-creator/templates/basic.mdfor instruction-only skillsskills/skill-creator/templates/advanced.mdfor skills with scripts
After authoring:
python scripts/validate_skill.py skills/{skill-name}
python scripts/package_skill.py skills/{skill-name}- Keep descriptions specific; they are the primary trigger for skill activation.
- Include usage triggers in the description ("Use this when ...").
- Place large references in references/ to keep SKILL.md concise.
- Prefer scripts for deterministic tasks.
The validator enforces Agent Skills best practices and the open spec:
- Name must be kebab-case, 1-64 characters, and match the folder name
- Description must be 1-1024 characters and include trigger keywords (use/when)
- Avoid reserved words in name/description (claude, anthropic)
- No XML/HTML tags in the description
- Frontmatter supports flat key/value pairs with inline lists/maps only; nested YAML and multi-line values are not supported
- Allowed frontmatter keys: name, description, license, compatibility, allowed-tools, metadata
- SKILL.md should be 500 lines or fewer
- Agent Skills best practices: platform.claude.com/docs/en/agents-and-tools/agent-skills/best-practices
- Anthropic skills repo: github.com/anthropics/skills
- Skill creator reference: github.com/anthropics/skills/tree/main/skills/skill-creator
- Awesome Claude Skills: github.com/ComposioHQ/awesome-claude-skills
- Open spec: agentskills.io/home
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