skill-creator

name	skill-creator
description	This skill should be used when creating, refining, or auditing Claude Code Skills, including SKILL.md structure, scaffolding, packaging, and best practices.
license	Complete terms in LICENSE.txt

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

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)
│   └── 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 (required)

Metadata Quality: The name and description in YAML frontmatter determine when Claude will use the skill. Be specific about what the skill does and when to use it. Use the third-person (e.g. "This skill should be used when..." instead of "Use this skill when...").

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
• Example: rotate_pdf.py for PDF rotation tasks (illustrative -- not included in this skill)
• Benefits: Token efficient, deterministic, may be executed without loading into context
• Note: Scripts may still need to be read by Claude for patching or environment-specific adjustments
• Node scripts in this repo: the repo root package.json is type:module, so a .js file using module.exports/require (CommonJS) fails at runtime with MODULE_NOT_FOUND (not at tsc). Name CommonJS helper/assert scripts .cjs (e.g. promptfoo custom asserts, which load via require); reserve .js/.mjs for genuine ESM. See knowledge-base/project/learnings/build-errors/2026-06-15-cjs-required-for-commonjs-scripts-and-promptfoo-harness-gotchas.md.

References (references/)

Documentation and reference material intended to be loaded as needed into context to inform Claude's process and thinking.

• When to include: For documentation that Claude should reference while working
• Examples: finance.md for financial schemas, mnda.md for company NDA template, policies.md for company policies, api_docs.md for API specifications
• Use cases: Database schemas, API documentation, domain knowledge, company policies, detailed workflow guides
• Benefits: Keeps SKILL.md lean, loaded only when Claude determines it's needed
• Best practice: If files are large (>10k words), include grep search patterns in SKILL.md
• Avoid duplication: Information should live in either SKILL.md or references files, not both. Prefer references files for detailed information unless it's truly core to the skill—this keeps SKILL.md lean while making information discoverable without hogging the context window. Keep only essential procedural instructions and workflow guidance in SKILL.md; move detailed reference material, schemas, and examples to references files.

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: logo.png for brand assets, slides.pptx for PowerPoint templates, frontend-template/ for HTML/React boilerplate, font.ttf for typography
• Use cases: Templates, images, icons, boilerplate code, fonts, sample documents that get copied or modified
• Benefits: Separates output resources from documentation, enables Claude to use files without loading them into context

Progressive Disclosure Design Principle

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 (Unlimited*)

*Unlimited because scripts can be executed without reading into context window.

Skill Creation Process

To create a skill, follow the "Skill Creation Process" in order, skipping steps only if there is a clear reason why they are not applicable.

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

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

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

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

To establish the skill's contents, analyze each concrete example to create a list of the reusable resources to include: scripts, references, and assets.

Step 3: Initializing 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 or packaging 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:

${CLAUDE_PLUGIN_ROOT:-plugins/soleur}/skills/skill-creator/scripts/init_skill.py <skill-name> --path <output-directory>

The script:

• Creates the skill directory at the specified path
• Generates a SKILL.md template with proper frontmatter and TODO placeholders
• Creates example resource directories: scripts/, references/, and assets/
• Adds example files in each directory that can be customized or deleted

After initialization, customize or remove the generated SKILL.md and example files as needed.

• Before writing a new skill description, run bun test plugins/soleur/test/components.test.ts to check the current word budget (1800 limit). Target 12-15 words for new skill descriptions — the budget is at 99% capacity as of 2026-04-05.
• After creating a new skill, manually add it to plugins/soleur/docs/_data/skills.js in the SKILL_CATEGORIES map -- skills are NOT auto-discovered, and missing this step silently removes the skill from the docs site with no build error.
• New agent files created mid-session cannot be invoked via subagent_type because the plugin registry is stale at session start; for live testing, use general-purpose agent type and embed the full instructions in the task prompt.

Step 4: Edit the Skill

When editing the (newly-generated or existing) skill, remember that the skill is being created for another instance of Claude to use. Focus on including information that would be beneficial and non-obvious to Claude. Consider what procedural knowledge, domain-specific details, or reusable assets would help another Claude instance execute these tasks more effectively.

Start with Reusable Skill Contents

To begin implementation, start with the reusable resources identified above: scripts/, references/, and assets/ files. Note that this step may require user input. For example, when implementing a brand-guidelines skill, the user may need to provide brand assets or templates to store in assets/, or documentation to store in references/.

Also, delete any example files and directories not needed for the skill. The initialization script creates example files in scripts/, references/, and assets/ to demonstrate structure, but most skills won't need all of them.

Update SKILL.md

Writing Style: Write the entire skill using imperative/infinitive form (verb-first instructions), not second person. Use objective, instructional language (e.g., "To accomplish X, do Y" rather than "You should do X" or "If you need to do X"). This maintains consistency and clarity for AI consumption.

To complete SKILL.md, answer the following questions:

1. What is the purpose of the skill, in a few sentences?
2. When should the skill be used?
3. In practice, how should Claude use the skill? All reusable skill contents developed above should be referenced so that Claude knows how to use them.

Step 5: Packaging a Skill

Once the skill is ready, it should be packaged into a distributable zip file that gets shared with the user. The packaging process automatically validates the skill first to ensure it meets all requirements:

${CLAUDE_PLUGIN_ROOT:-plugins/soleur}/skills/skill-creator/scripts/package_skill.py <path/to/skill-folder>

Optional output directory specification:

${CLAUDE_PLUGIN_ROOT:-plugins/soleur}/skills/skill-creator/scripts/package_skill.py <path/to/skill-folder> ./dist

The packaging script will:

1. Validate the skill automatically, checking:

   • YAML frontmatter format and required fields
   • Skill naming conventions and directory structure
   • Description completeness and quality
   • File organization and resource references

2. Package the skill if validation passes, creating a zip file named after the skill (e.g., my-skill.zip) that includes all files and maintains the proper directory structure for distribution.

If validation fails, the script will report the errors and exit without creating a package. Fix any validation errors and run the packaging command again.

Step 5b: Security scan (cooperative-fast-path)

After package_skill.py validates the structure but BEFORE the zip is distributed, invoke the skill-security-scan advisory gate against the newly-scaffolded SKILL.md:

bash ${CLAUDE_PLUGIN_ROOT:-plugins/soleur}/skills/skill-security-scan/scripts/run-scan.sh < <skill-folder>/SKILL.md

Operator handling:

• LOW-RISK — proceed with packaging.
• REVIEW — present findings as informational; ask operator to confirm before packaging.
• HIGH-RISK — present findings + override instructions referencing skill-security-scan/references/override-mechanism.md. Block packaging until either (a) the SKILL.md is revised, or (b) a valid override artifact is committed under knowledge-base/engineering/security/skill-overrides/.

The PreToolUse hook on Write (.claude/hooks/skill-security-scan-write.sh) is the load-bearing gate at the tool layer — this Step 5b is the operator-friendly cooperative-fast-path that surfaces findings early.

Step 6: Iterate

After testing the skill, users may request improvements. Often this happens right after using the skill, with fresh context of how the skill performed.

Iteration workflow:

1. Use the skill on real tasks
2. Notice struggles or inefficiencies
3. Identify how SKILL.md or bundled resources should be updated
4. Implement changes and test again

Sharp Edges

• When a SKILL.md prose fence documents shell-active patterns by design (e.g., bash -c "$VAR", process substitution, an eval-style invocation), label the fence ```text instead of ```bash and document the load-bearing mitigations (timeout, reject-regex, env scrub, trust source) in a per-skill Sharp Edges section. Otherwise the skill-security-scan calibration suite fails the first-party SKILL.md with HIGH-RISK on code-execution — there is no per-finding override mechanism for first-party legitimate uses. The fence is documentation; the orchestrator still dispatches via the Bash tool when it reads the prose, so runtime behavior is unchanged. See knowledge-base/project/learnings/2026-05-20-skill-md-shell-active-prose-calibration-carve-out.md.

Auditing Existing Skills

For auditing and improving existing skills, see the audit-skill workflow.

Reference Files

For detailed guidance on skill authoring, see:

• official-spec.md - Anthropic's official skill specification
• best-practices.md - Skill authoring best practices
• core-principles.md - Core principles for skill design
• skill-structure.md - Skill structure and organization
• recommended-structure.md - Recommended file structure
• common-patterns.md - Common skill patterns (template, workflow, conditional)
• be-clear-and-direct.md - Writing clear skill instructions
• executable-code.md - Working with executable code in skills
• using-scripts.md - Using scripts in skills
• using-templates.md - Using templates in skills
• iteration-and-testing.md - Iteration and testing guidance
• workflows-and-validation.md - Workflow and validation patterns
• api-security.md - API security considerations
• fail-closed redaction pattern - Designing output paths for skills that generate user-derived artifacts intended for external sharing

Workflows

Step-by-step guides for specific skill authoring tasks:

• create-new-skill.md - Create a new skill from scratch
• audit-skill.md - Audit an existing skill against best practices
• add-reference.md - Add a reference file to a skill
• add-script.md - Add a script to a skill
• add-template.md - Add a template to a skill
• add-workflow.md - Add a workflow to a skill
• create-domain-expertise-skill.md - Create a domain expertise skill
• upgrade-to-router.md - Upgrade a simple skill to a router skill
• verify-skill.md - Verify a skill meets requirements
• get-guidance.md - Get guidance on skill design decisions

Templates

Starter templates for common skill types:

• simple-skill.md - Template for a simple single-file skill
• router-skill.md - Template for a multi-workflow router skill