skill-optimizer

# 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. Skills follow the [Agent Skills](https://agentskills.io/) open standard, with Claude Code extensions for invocation control, subagent execution, and dynamic context injection. ### 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 │ └── Markdown instructions └── Bundled Resources (optional) ├── scripts/ - Executable code (Python/Bash/etc.) ├── references/ - Documentation loaded into context as needed └── assets/ - Files used in output (templates, icons, fonts) ``` #### 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..."). **Frontmatter Fields:** | Field | Required | Description | |-------|----------|-------------| | `name` | No | Display name (max 64 chars, lowercase + hyphens). Defaults to directory name. | | `description` | Recommended | What the skill does and when to use it (max 1024 chars). | | `argument-hint` | No | Hint shown during autocomplete (e.g., `[issue-number]`). | | `disable-model-invocation` | No | `true` = only user can invoke via `/name`. | | `user-invocable` | No | `false` = hide from `/` menu (Claude-only background knowledge). | | `allowed-tools` | No | Restrict tools when skill is active (e.g., `Read, Grep, Glob`). | | `model` | No | Model override when skill is active. | | `context` | No | `fork` = run in isolated subagent. | | `agent` | No | Subagent type: `Explore`, `Plan`, `general-purpose`, or custom from `.claude/agents/`. | | `hooks` | No | Scoped hooks for skill lifecycle. See [Hooks docs](https://code.claude.com/docs/en/hooks). | **Example with all fields:** ```yaml --- name: deploy-production description: Deploy the application to production. Use after all tests pass. argument-hint: [environment] disable-model-invocation: true allowed-tools: Bash(deploy:*), Read context: fork agent: general-purpose --- ``` ### String Substitutions Skills support dynamic value substitution in the markdown content: | Variable | Description | |----------|-------------| | `$ARGUMENTS` | All arguments passed when invoking (e.g., `/my-skill arg1 arg2`) | | `${CLAUDE_SESSION_ID}` | Current session ID for logging or session-specific files | If `$ARGUMENTS` is not present in content, arguments are appended as `ARGUMENTS: <value>`. **Example:** ```markdown --- name: fix-issue description: Fix a GitHub issue disable-model-invocation: true --- Fix GitHub issue $ARGUMENTS following our coding standards. Log progress to logs/${CLAUDE_SESSION_ID}.log ``` ### Dynamic Context Injection The exclamation-backtick syntax runs shell commands before skill content reaches Claude. The command output replaces the placeholder. **Syntax:** exclamation mark followed by backtick-wrapped command: `EXCLAIM` + `BACKTICK command BACKTICK` **Example skill content:** ``` ## PR Context - Diff: EXCLAIM-BACKTICK gh pr diff BACKTICK - Comments: EXCLAIM-BACKTICK gh pr view --comments BACKTICK - Changed files: EXCLAIM-BACKTICK gh pr diff --name-only BACKTICK Summarize this pull request... ``` (Replace EXCLAIM with the exclamation mark character and BACKTICK with the backtick character in real skills) When this skill runs: 1. Each exclamation-backtick command executes immediately (before Claude sees anything) 2. The output replaces the placeholder in the skill content 3. Claude receives the fully-rendered prompt with actual data This is preprocessing, not something Claude executes. Claude only sees the final result. ### Invocation Control By default, both users and Claude can invoke any skill. Two frontmatter fields control this: | Frontmatter | User can invoke | Claude can invoke | In context | |-------------|-----------------|-------------------|------------| | (default) | Yes | Yes | Description always visible | | `disable-model-invocation: true` | Yes | No | Description hidden from Claude | | `user-invocable: false` | No | Yes | Description always visible | **When to use each:** - **`disable-model-invocation: true`**: For workflows with side effects (deploy, commit, send-message). Prevents Claude from triggering automatically. - **`user-invocable: false`**: For background knowledge that isn't a meaningful command (e.g., `legacy-system-context`). Claude should know this when relevant, but `/legacy-system-context` isn't useful for users. ### Subagent Integration Add `context: fork` to run skills in isolation. The skill content becomes the subagent's prompt (no conversation history access). ```yaml --- name: deep-research description: Research a topic thoroughly context: fork agent: Explore --- Research $ARGUMENTS thoroughly: 1. Find relevant files using Glob and Grep 2. Read and analyze the code 3. Summarize findings with specific file references ``` **Agent options:** | Agent | Description | |-------|-------------| | `Explore` | Read-only codebase exploration (Glob, Grep, Read) | | `Plan` | Architecture planning and design | | `general-purpose` | Full capabilities (default) | | Custom | Any agent from `.claude/agents/` | **Note:** `context: fork` only makes sense for skills with explicit instructions. Guidelines-only skills (e.g., "use these API conventions") receive no actionable prompt and return without meaningful output. ### Skill Locations Where a skill is stored determines who can use it: | Location | Path | Applies to | Priority | |----------|------|------------|----------| | Enterprise | Managed settings | All org users | Highest | | Personal | `~/.claude/skills/<name>/SKILL.md` | All your projects | High | | Project | `.claude/skills/<name>/SKILL.md` | This project only | Medium | | Plugin | `<plugin>/skills/<name>/SKILL.md` | Where plugin enabled | Namespaced | When skills share the same name, higher-priority locations win. Plugin skills use `plugin-name:skill-name` namespace, so they cannot conflict. **Nested discovery:** When editing files in subdirectories (e.g., `packages/frontend/`), Claude Code also discovers skills from nested `.claude/skills/` directories. This supports monorepos where packages have their own skills. **Legacy commands:** Files in `.claude/commands/` still work with the same frontmatter. Skills are recommended since they support additional features like supporting files. #### Bundled Resources (optional) ##### Scripts (`scripts/`) **Content Type: Code** - 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, **script code never enters context - only output does** - **Key advantage**: A 200-line script only costs ~20 tokens (the output), not 2000+ tokens (the code) - **Note**: Scripts may still need to be read by Claude for patching or environment-specific adjustments ##### References (`references/`) **Content Type: Instructions** - 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/`) **Content Type: Resources** - 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: | Level | When Loaded | Token Cost | Content | |-------|-------------|------------|---------| | **Level 1: Metadata** | Always (at startup) | ~100 tokens per Skill | `name` and `description` from YAML frontmatter | | **Level 2: Instructions** | When Skill is triggered | Under 5k tokens | SKILL.md body with instructions and guidance | | **Level 3+: Resources** | As needed | Effectively unlimited* | Bundled files executed via bash without loading into context | *Scripts are executed without loading code into context (only output enters context). Reference files and assets are loaded only when Claude explicitly accesses them via bash commands. **Key insight**: You can install dozens of Skills with minimal context penalty. Claude only knows each Skill exists and when to use it until one is triggered. **Context budget**: Skill descriptions are loaded into context so Claude knows what's available. If you have many skills, they may exceed the character budget (default 15,000 characters). Run `/context` to check for excluded skills. To increase the limit, set `SLASH_COMMAND_TOOL_CHAR_BUDGET` environment variable. ### The Skills Filesystem Architecture Skills exist as directories on the local filesystem, and Claude interacts with them using bash commands and file operations. **How Claude accesses Skill content:** 1. **Reading instructions**: When a Skill is triggered, Claude reads SKILL.md from the filesystem via bash, bringing its instructions into context 2. **Loading references**: If instructions reference other files (like `references/api_docs.md` or database schemas), Claude reads those files using additional bash commands 3. **Executing scripts**: When instructions mention executable scripts, Claude runs them via bash. **Only the script output enters context, not the code itself** **What this enables:** - **On-demand file access**: Claude reads only the files needed for each task. A Skill can include dozens of reference files, but if your task only needs one schema, Claude loads just that file. The rest consume zero tokens - **Efficient script execution**: When Claude runs `validate_form.py`, only the output consumes tokens, not the 200-line script. This makes scripts far more efficient than having Claude generate equivalent code on the fly - **No practical limit on bundled content**: Because files don't consume context until accessed, Skills can include comprehensive documentation, datasets, examples, or reference materials without context penalty **Example workflow:** ``` 1. User: "Process this PDF and extract tables" 2. Claude: bash: read pdf-skill/SKILL.md 3. SKILL.md mentions scripts/extract_tables.py 4. Claude: bash: python scripts/extract_tables.py input.pdf 5. Script output: "Extracted 3 tables: [table data...]" 6. Claude proceeds using the extracted data (script code never entered context) ``` ## 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. Conduct a structured interview using the protocol in `references/interview-protocol.md`, which provides 6 required questions, probing follow-ups, and explicit pushback rules for when answers are too vague. The most important question: **What does Claude get wrong today without this skill?** If Claude already handles the task well, the skill is not worth building. Every failure mode surfaced becomes a gotcha entry -- the highest-signal content any skill can contain. To avoid overwhelming users, ask questions one at a time, starting with the most important. Conclude this step when you have concrete use cases, a failure mode inventory, and verifiable success criteria (see exit criteria in `references/interview-protocol.md`). ### 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. #### Category Identification Identify which of the 9 skill categories this skill belongs to (see `references/skill-categories.md` for the full taxonomy with examples and structural guidance): 1. Library & API Reference 2. Product Verification 3. Data Fetching & Analysis 4. Code Scaffolding & Templates 5. Code Quality & Review 6. CI/CD & Deployment 7. Runbooks 8. Business Process & Team Automation 9. Infrastructure Operations Present the categories and ask the user to confirm. The best skills fit cleanly into one category. If the skill straddles two, flag it -- it may need to be split. The category informs the skill's structural pattern and eval strategy. ### 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: ```bash 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. ### 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