skill-development

name skill-development description This skill should be used when the user wants to "create a skill", "add a skill to plugin", "write a new skill", "improve skill description", "organize skill content", or needs guidance on skill structure, progressive disclosure, or skill development best practices for Claude Code plugins. version 0.1.0 Skill Development for Claude Code Plugins This skill provides guidance for creating effective skills for Claude Code plugins. 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 Specialized workflows - Multi-step procedures for specific domains Tool integrations - Instructions for working with specific file formats or APIs Domain expertise - Company-specific knowledge, schemas, business logic 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 : scripts/rotate_pdf.py for PDF rotation tasks 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 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 : references/finance.md for financial schemas, references/mnda.md for company NDA template, references/policies.md for company policies, references/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 : assets/logo.png for brand assets, assets/slides.pptx for PowerPoint templates, assets/frontend-template/ for HTML/React boilerplate, assets/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: Metadata (name + description) - Always in context (~100 words) SKILL.md body - When skill triggers (<5k words) 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: Considering how to execute on the example from scratch 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: Rotating a PDF requires re-writing the same code each time 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: Writing a frontend webapp requires the same boilerplate HTML/React each time 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: Querying BigQuery requires re-discovering the table schemas and relationships each time A references/schema.md file documenting the table schemas would be helpful to store in the skill For Claude Code plugins: When building a hooks skill, the analysis shows: Developers repeatedly need to validate hooks.json and test hook scripts scripts/validate-hook-schema.sh and scripts/test-hook.sh utilities would be helpful references/patterns.md for detailed hook patterns to avoid bloating SKILL.md 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: Create Skill Structure For Claude Code plugins, create the skill directory structure: mkdir -p plugin-name/skills/skill-name/{references,examples,scripts} touch plugin-name/skills/skill-name/SKILL.md Note: Unlike the generic skill-creator which uses init_skill.py , plugin skills are created directly in the plugin's skills/ directory with a simpler manual structure. Step 4: Edit the Skill When editing the (newly-created 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. Create only the directories you actually need (references/, examples/, scripts/). 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. Description (Frontmatter): Use third-person format with specific trigger phrases: --- name: Skill Name description: This skill should be used when the user asks to "specific phrase 1" , "specific phrase 2" , "specific phrase 3" . Include exact phrases users would say that should trigger this skill. Be concrete and specific. version: 0.1 .0 --- Good description examples: description: This skill should be used when the user asks to "create a hook" , "add a PreToolUse hook" , "validate tool use" , "implement prompt-based hooks" , or mentions hook events (PreToolUse, PostToolUse, Stop). Bad description examples: description: Use this skill when working with hooks. # Wrong person, vague description: Load when user needs hook help. # Not third person description: Provides hook guidance. # No trigger phrases To complete SKILL.md body, answer the following questions: What is the purpose of the skill, in a few sentences? When should the skill be used? (Include this in frontmatter description with specific triggers) 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. Keep SKILL.md lean: Target 1,500-2,000 words for the body. Move detailed content to references/: Detailed patterns → references/patterns.md Advanced techniques → references/advanced.md Migration guides → references/migration.md API references → references/api-reference.md Reference resources in SKILL.md: ## Additional Resources ### Reference Files For detailed patterns and techniques, consult: - **`references/patterns.md`** - Common patterns - **`references/advanced.md`** - Advanced use cases ### Example Files Working examples in `examples/` : - **`example-script.sh`** - Working example Step 5: Validate and Test For plugin skills, validation is different from generic skills: Check structure : Skill directory in plugin-name/skills/skill-name/ Validate SKILL.md : Has frontmatter with name and description Check trigger phrases : Description includes specific user queries Verify writing style : Body uses imperative/infinitive form, not second person Test progressive disclosure : SKILL.md is lean (~1,500-2,000 words), detailed content in references/ Check references : All referenced files exist Validate examples : Examples are complete and correct Test scripts : Scripts are executable and work correctly Use the skill-reviewer agent: Ask: "Review my skill and check if it follows best practices" The skill-reviewer agent will check description quality, content organization, and progressive disclosure. 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: Use the skill on real tasks Notice struggles or inefficiencies Identify how SKILL.md or bundled resources should be updated Implement changes and test again Common improvements: Strengthen trigger phrases in description Move long sections from SKILL.md to references/ Add missing examples or scripts Clarify ambiguous instructions Add edge case handling Plugin-Specific Considerations Skill Location in Plugins Plugin skills live in the plugin's skills/ directory: my-plugin/ ├── .claude-plugin/ │ └── plugin.json ├── commands/ ├── agents/ └── skills/ └── my-skill/ ├── SKILL.md ├── references/ ├── examples/ └── scripts/ Auto-Discovery Claude Code automatically discovers skills: Scans skills/ directory Finds subdirectories containing SKILL.md Loads skill metadata (name + description) always Loads SKILL.md body when skill triggers Loads references/examples when needed No Packaging Needed Plugin skills are distributed as part of the plugin, not as separate ZIP files. Users get skills when they install the plugin. Testing in Plugins Test skills by installing plugin locally: # Test with --plugin-dir cc --plugin-dir /path/to/plugin # Ask questions that should trigger the skill # Verify skill loads correctly Examples from Plugin-Dev Study the skills in this plugin as examples of best practices: hook-development skill: Excellent trigger phrases: "create a hook", "add a PreToolUse hook", etc. Lean SKILL.md (1,651 words) 3 references/ files for detailed content 3 examples/ of working hooks 3 scripts/ utilities agent-development skill: Strong triggers: "create an agent", "agent frontmatter", etc. Focused SKILL.md (1,438 words) References include the AI generation prompt from Claude Code Complete agent examples plugin-settings skill: Specific triggers: "plugin settings", ".local.md files", "YAML frontmatter" References show real implementations (multi-agent-swarm, ralph-loop) Working parsing scripts Each demonstrates progressive disclosure and strong triggering. Progressive Disclosure in Practice What Goes in SKILL.md Include (always loaded when skill triggers): Core concepts and overview Essential procedures and workflows Quick reference tables Pointers to references/examples/scripts Most common use cases Keep under 3,000 words, ideally 1,500-2,000 words What Goes in references/ Move to references/ (loaded as needed): Detailed patterns and advanced techniques Comprehensive API documentation Migration guides Edge cases and troubleshooting Extensive examples and walkthroughs Each reference file can be large (2,000-5,000+ words) What Goes in examples/ Working code examples: Complete, runnable scripts Configuration files Template files Real-world usage examples Users can copy and adapt these directly What Goes in scripts/ Utility scripts: Validation tools Testing helpers Parsing utilities Automation scripts Should be executable and documented Writing Style Requirements Imperative/Infinitive Form Write using verb-first instructions, not second person: Correct (imperative): To create a hook, define the event type. Configure the MCP server with authentication. Validate settings before use. Incorrect (second person): You should create a hook by defining the event type. You need to configure the MCP server. You must validate settings before use. Third-Person in Description The frontmatter description must use third person: Correct: description: This skill should be used when the user asks to "create X" , "configure Y" ... Incorrect: description: Use this skill when you want to create X... description: Load this skill when user asks... Objective, Instructional Language Focus on what to do, not who should do it: Correct: Parse the frontmatter using sed. Extract fields with grep. Validate values before use. Incorrect: You can parse the frontmatter... Claude should extract fields... The user might validate values... Validation Checklist Before finalizing a skill: Structure: SKILL.md file exists with valid YAML frontmatter Frontmatter has name and description fields Markdown body is present and substantial Referenced files actually exist Description Quality: Uses third person ("This skill should be used when...") Includes specific trigger phrases users would say Lists concrete scenarios ("create X", "configure Y") Not vague or generic Content Quality: SKILL.md body uses imperative/infinitive form Body is focused and lean (1,500-2,000 words ideal, <5k max) Detailed content moved to references/ Examples are complete and working Scripts are executable and documented Progressive Disclosure: Core concepts in SKILL.md Detailed docs in references/ Working code in examples/ Utilities in scripts/ SKILL.md references these resources Testing: Skill triggers on expected user queries Content is helpful for intended tasks No duplicated information across files References load when needed Common Mistakes to Avoid Mistake 1: Weak Trigger Description ❌ Bad: description: Provides guidance for working with hooks. Why bad: Vague, no specific trigger phrases, not third person ✅ Good: description: This skill should be used when the user asks to "create a hook" , "add a PreToolUse hook" , "validate tool use" , or mentions hook events. Provides comprehensive hooks API guidance. Why good: Third person, specific phrases, concrete scenarios Mistake 2: Too Much in SKILL.md ❌ Bad: skill-name/