Skill Creator

Skill Creator

This skill provides guidance for creating effective skills using the existing tool system.

About Skills

Skills are modular, self-contained packages that extend the agent's capabilities by providing specialized knowledge, workflows, and tools. They transform a general-purpose agent into a specialized agent equipped with procedural knowledge.

What Skills Provide

1. Specialized workflows - Multi-step procedures for specific domains
2. Tool integrations - Instructions for working with specific file formats or APIs
3. Domain expertise - Company-specific knowledge, schemas, business logic
4. Bundled resources - Scripts, references, and assets for complex tasks

Core Principle

Concise is Key: Only add context the agent doesn't already have. Challenge each piece of information: "Does this justify its token cost?" Prefer concise examples over verbose explanations.

Skill Structure

Every skill consists of a required SKILL.md file and optional bundled resources:

skill-name/
├── SKILL.md (required)
│   ├── YAML frontmatter metadata (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.)

SKILL.md Components

Frontmatter (YAML) - Required fields:

• name: Skill name in hyphen-case (e.g., weather-api, pdf-editor)
• description: CRITICAL - Primary triggering mechanism
  • Must clearly describe what the skill does
  • Must explicitly state when to use it
  • Include specific trigger scenarios and keywords
  • All "when to use" info goes here, NOT in body
  • Example: "PDF document processing with rotation, merging, splitting, and text extraction. Use when user needs to: (1) Rotate PDF pages, (2) Merge multiple PDFs, (3) Split PDF files, (4) Extract text from PDFs."

Body (Markdown) - Loaded after skill triggers:

• Detailed usage instructions
• How to call scripts and read references
• Examples and best practices
• Use imperative/infinitive form ("Use X to do Y")

Bundled Resources

scripts/ - When to include:

• Code is repeatedly rewritten
• Deterministic execution needed (avoid LLM randomness)
• Examples: PDF rotation, image processing
• Must test scripts before including

references/ - When to include:

• ONLY when documentation is too large for SKILL.md (>500 lines)
• Database schemas, complex API specs that agent needs to reference
• Agent reads these files into context as needed
• NOT for: API reference docs, usage examples, tutorials (put in SKILL.md instead)
• Rule of thumb: If it fits in SKILL.md, don't create a separate reference file

assets/ - When to include:

• Files used in output (not loaded to context)
• Templates, icons, boilerplate code
• Copied or modified in final output

Important: Most skills don't need all three. Choose based on actual needs.

What NOT to Include

Do NOT create auxiliary documentation files:

• README.md - Instructions belong in SKILL.md
• INSTALLATION_GUIDE.md - Setup info belongs in SKILL.md
• CHANGELOG.md - Not needed for local skills
• API_REFERENCE.md - Put API docs directly in SKILL.md
• USAGE_EXAMPLES.md - Put examples directly in SKILL.md
• Any other documentation files - Everything goes in SKILL.md unless it's too large

Critical Rule: Only create files that the agent will actually execute (scripts) or that are too large for SKILL.md (references). Documentation, examples, and guides ALL belong in SKILL.md.

Installing a Skill

Install target directory: <workspace>/skills/<name>/ (the <workspace> is from the "Workspace" section).

Step 1 — Obtain skill content

Step 2 — Identify and install

1. Locate the SKILL.md (may be at top level or inside a subdirectory)
2. Extract name from YAML frontmatter
3. Copy the entire skill directory (SKILL.md and all sibling files/folders such as references/, scripts/, assets/, etc.) into <workspace>/skills/<name>/
4. If an install/setup file exists (e.g. INSTALL.md), follow its instructions — the final result must still end up in <workspace>/skills/<name>/

Skill Creation Process (from scratch)

1. Understand - Clarify use cases with concrete examples
2. Plan - Identify needed scripts, references, assets
3. Initialize - Run init_skill.py to create template
4. Edit - Implement SKILL.md and resources
5. Validate (optional) - Run quick_validate.py to check format
6. Iterate - Improve based on real usage

Skill Naming

• Use lowercase letters, digits, and hyphens only; normalize user-provided titles to hyphen-case (e.g., "Plan Mode" -> plan-mode).
• When generating names, generate a name under 64 characters (letters, digits, hyphens).
• Prefer short, verb-led phrases that describe the action.
• Namespace by tool when it improves clarity or triggering (e.g., gh-address-comments, linear-address-issue).
• Name the skill folder exactly after the skill name.

Step-by-Step Guide

Step 1: Understanding the Skill with Concrete Examples

Skip this step only when the skill's usage patterns are already clearly understood. It remains valuable even when working with an existing skill.

To create an effective skill, clearly understand concrete examples of how the skill will be used. This understanding can come from either direct user examples or generated examples that are validated with user feedback.

For example, when building an image-editor skill, relevant questions include:

• "What functionality should the image-editor skill support? Editing, rotating, anything else?"
• "Can you give some examples of how this skill would be used?"
• "I can imagine users asking for things like 'Remove the red-eye from this image' or 'Rotate this image'. Are there other ways you imagine this skill being used?"
• "What would a user say that should trigger this skill?"

To avoid overwhelming users, avoid asking too many questions in a single message. Start with the most important questions and follow up as needed for better effectiveness.

Conclude this step when there is a clear sense of the functionality the skill should support.

Step 2: Planning the Reusable Skill Contents

To turn concrete examples into an effective skill, analyze each example by:

1. Considering how to execute on the example from scratch
2. Identifying what scripts, references, and assets would be helpful when executing these workflows repeatedly

Planning Checklist:

• ✅ Always needed: SKILL.md with clear description and usage instructions
• ✅ scripts/: Only if code needs to be executed (not just shown as examples)
• ❌ references/: Rarely needed - only if documentation is >500 lines and can't fit in SKILL.md
• ✅ assets/: Only if files are used in output (templates, boilerplate, etc.)

Example: When building a pdf-editor skill to handle queries like "Help me rotate this PDF," the analysis shows:

1. Rotating a PDF requires re-writing the same code each time
2. A scripts/rotate_pdf.py script would be helpful to store in the skill
3. ❌ Don't create references/api-docs.md - put API info in SKILL.md instead

Example: When designing a frontend-webapp-builder skill for queries like "Build me a todo app" or "Build me a dashboard to track my steps," the analysis shows:

1. Writing a frontend webapp requires the same boilerplate HTML/React each time
2. An assets/hello-world/ template containing the boilerplate HTML/React project files would be helpful to store in the skill
3. ❌ Don't create references/usage-examples.md - put examples in SKILL.md instead

Example: When building a big-query skill to handle queries like "How many users have logged in today?" the analysis shows:

1. Querying BigQuery requires re-discovering the table schemas and relationships each time
2. A references/schema.md file documenting the table schemas would be helpful to store in the skill (ONLY because schemas are very large)
3. ❌ Don't create separate references/query-examples.md - put examples in SKILL.md instead

To establish the skill's contents, analyze each concrete example to create a list of the reusable resources to include: scripts, references, and assets. Default to putting everything in SKILL.md unless there's a compelling reason to separate it.

Step 3: Initialize the Skill

At this point, it is time to actually create the skill.

Skip this step only if the skill being developed already exists, and iteration is needed. In this case, continue to the next step.

When creating a new skill from scratch, always run the init_skill.py script. The script conveniently generates a new template skill directory that automatically includes everything a skill requires, making the skill creation process much more efficient and reliable.

Usage:

scripts/init_skill.py <skill-name> --path <output-directory> [--resources scripts,references,assets] [--examples]

Examples:

scripts/init_skill.py my-skill --path <workspace>/skills
scripts/init_skill.py my-skill --path <workspace>/skills --resources scripts,references
scripts/init_skill.py my-skill --path <workspace>/skills --resources scripts --examples

Where <workspace> is your workspace directory shown in the "Workspace" section of the system prompt.

The script:

• Creates the skill directory at the specified path
• Generates a SKILL.md template with proper frontmatter and TODO placeholders
• Optionally creates resource directories based on --resources
• Optionally adds example files when --examples is set

After initialization, customize the SKILL.md and add resources as needed. If you used --examples, replace or delete placeholder files.

Important: Always create skills in workspace skills directory (<workspace>/skills), NOT in project directory. Check the "Workspace" section for the actual workspace path.