Skill Creator

Skill Creator

This skill provides guidance for creating effective skills.

About Skills

Skills are modular, self-contained packages that extend Claude's capabilities by providing specialized knowledge, workflows, and tools. Think of them as "onboarding guides" for specific domains or tasks—they transform Claude from a general-purpose agent into a specialized agent equipped with procedural knowledge that no model can fully possess.

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 and repetitive tasks

Core Principles

Concise is Key

The context window is a public good. Skills share the context window with everything else Claude needs: system prompt, conversation history, other Skills' metadata, and the actual user request.

Default assumption: Claude is already very smart. Only add context Claude doesn't already have. Challenge each piece of information: "Does Claude really need this explanation?" and "Does this paragraph justify its token cost?"

Prefer concise examples over verbose explanations.

Set Appropriate Degrees of Freedom

Match the level of specificity to the task's fragility and variability:

High freedom (text-based instructions): Use when multiple approaches are valid, decisions depend on context, or heuristics guide the approach.

Medium freedom (pseudocode or scripts with parameters): Use when a preferred pattern exists, some variation is acceptable, or configuration affects behavior.

Low freedom (specific scripts, few parameters): Use when operations are fragile and error-prone, consistency is critical, or a specific sequence must be followed.

Think of Claude as exploring a path: a narrow bridge with cliffs needs specific guardrails (low freedom), while an open field allows many routes (high freedom).

Anatomy of a Skill

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)
│   │   ├── argument-hint: (optional)
│   │   └── disable-model-invocation: (optional)
│   └── Markdown instructions (required)
└── Bundled Resources (optional)
    ├── scripts/          - Executable code (Python/Bash/etc.)
    ├── references/       - Documentation loaded into context as needed
    └── assets/           - Files used in output (templates, icons, fonts, etc.)

SKILL.md (required)

Every SKILL.md consists of:

• Frontmatter (YAML): Contains name and description fields (required). These are the only fields that Claude reads to determine when the skill gets used, thus it is very important to be clear and comprehensive in describing what the skill is, and when it should be used. Optional fields:
  • argument-hint: Hint text shown after the slash command (e.g., "[file-or-pattern]"). Helps users understand what arguments the skill accepts.
  • disable-model-invocation: Set to true to prevent the model from invoking this skill automatically. Use for skills that modify state (git operations, deployments) where manual invocation is preferred.
  • allowed-tools: Restrict which tools the skill can use.
  • model: Override the default model.
• Body (Markdown): Instructions and guidance for using the skill. Only loaded AFTER the skill triggers (if at all).

Bundled Resources (optional)

Scripts (scripts/)

Executable code (Python/Bash/etc.) for tasks that require deterministic reliability or are repeatedly rewritten.

• When to include: When the same code is being rewritten repeatedly or deterministic reliability is needed
• Benefits: Token efficient, deterministic, may be executed without loading into context

References (references/)

Documentation and reference material intended to be loaded as needed into context.

• When to include: For documentation that Claude should reference while working
• Examples: Database schemas, API documentation, domain knowledge, company policies
• Best practice: If files are large (>10k words), include grep search patterns in SKILL.md

Assets (assets/)

Files not intended to be loaded into context, but rather used within the output Claude produces.

• When to include: When the skill needs files that will be used in the final output
• Examples: Templates, images, icons, boilerplate code, fonts

What to Not Include in a Skill

Do NOT create extraneous documentation files:

• README.md
• INSTALLATION_GUIDE.md
• QUICK_REFERENCE.md
• CHANGELOG.md

The skill should only contain information needed for an AI agent to do the job.

Progressive Disclosure

Skills use a three-level loading system to manage context efficiently:

1. Metadata (name + description) - Always in context (~100 words)
2. SKILL.md body - When skill triggers (<5k words)
3. Bundled resources - As needed by Claude

Keep SKILL.md body under 500 lines. Split content into separate files when approaching this limit.

Skill Creation Process

1. Understand the skill with concrete examples
2. Plan reusable skill contents (scripts, references, assets)
3. Initialize the skill (run init_skill.py)
4. Edit the skill (implement resources and write SKILL.md)
5. Package the skill (run package_skill.py)
6. Iterate based on real usage

Step 1: Understanding with Concrete Examples

Ask questions like:

• "What functionality should this skill support?"
• "Can you give some examples of how this skill would be used?"
• "What would a user say that should trigger this skill?"

Step 2: Planning Reusable Contents

For each example, analyze:

1. How to execute from scratch
2. What scripts, references, and assets would be helpful for repeated execution

Step 3: Initializing the Skill

Run the init script:

python scripts/init_skill.py <skill-name> --path <output-directory>

This creates the skill directory with SKILL.md template and example resource directories.

Step 4: Edit the Skill

Consult these guides based on your skill's needs:

• Multi-step processes: See references/workflows.md
• Specific output formats: See references/output-patterns.md

Writing Guidelines

• Always use imperative/infinitive form
• The description field is the primary triggering mechanism
• Include all "when to use" information in description, not body

Step 5: Package the Skill

python scripts/package_skill.py <path/to/skill-folder> [output-directory]

This validates and packages the skill into a .skill file.

Step 5.5: Add Pattern Evaluation Step

Every new skill should include a final step that evaluates whether reusable patterns were discovered during execution. Add this as the last step in the skill's Instructions:

### Step N (Final): Evaluate Reusable Patterns

Run the **pattern-evaluator** agent to assess whether any reusable patterns (rules, skills, or agents) were discovered during this session and should be persisted.

Step 6: Iterate

1. Use the skill on real tasks
2. Notice struggles or inefficiencies
3. Update SKILL.md or bundled resources
4. Test again