Agent Skills Creator

Agent Skills Creator

Create skills that follow the Agent Skills open format. Covers the full lifecycle from pattern selection through validation and README update.

Reference Files

Choose a Skill Category

Determine what type of problem the skill solves. Category informs pattern choice.

Load references/skill-categories.md for detailed guidance per category including authoring tips and examples.

Choose a Skill Pattern

Decision guide:

• Auditing or linting against a checklist: rules-based
• Guiding a multi-step process: workflow
• Dispatching to different tracks by context: simple/hub
• Unsure: start with workflow (most flexible)

Load references/skill-patterns.md for structural templates and skeletons of each pattern.

Creation Workflow

Copy this checklist to track progress:

Skill creation progress:
- [ ] Step 1: Choose skill category and pattern
- [ ] Step 2: Create directory and frontmatter
- [ ] Step 3: Write SKILL.md body
- [ ] Step 4: Add reference or rule files
- [ ] Step 5: Validate with quality checklist
- [ ] Step 6: Update README.md
- [ ] Step 7: Smoke-test installation
- [ ] Step 8: Evaluate and iterate

Step 1: Choose skill category and pattern

First determine the category (what problem the skill solves), then pick the structural pattern. Load references/skill-categories.md for category guidance and references/skill-patterns.md for structural templates.

Step 2: Create directory and frontmatter

Load references/format-specification.md for hard constraints.

• Create skills/<name>/SKILL.md
• Folder name must match name field (kebab-case)
• name: max 64 chars, lowercase letters/numbers/hyphens, no "anthropic" or "claude"
• description: max 1024 chars, third-person voice, include "Use when..." triggers with specific keywords

Step 3: Write SKILL.md body

• Keep under 500 lines; split into reference files if longer
• Only add context Claude does not already have (see "Don't State the Obvious" in references/authoring-tips.md)
• Use consistent terminology throughout
• Match degrees of freedom to task fragility — prose for open-ended work, specific scripts for fragile or destructive operations (see "Degrees of Freedom" in references/authoring-tips.md)
• Reach for named content patterns when they fit: template for fixed output, examples for format-sensitive output, conditional for decision points
• Include a copyable progress checklist for multi-step workflows
• Include validation/feedback loops for quality-critical tasks
• Build a Gotchas section from observed failure points — this is the highest-signal content
• Load references/authoring-tips.md for content strategy guidance on voice, degrees of freedom, content patterns, descriptions, and more

Step 4: Add reference or rule files

Workflow/mixed pattern: add references/ folder with focused files. Link each from SKILL.md with "Read when..." guidance in a table.

Rules-based pattern: add rules/ folder. Load references/rules-folder-structure.md for the _sections.md, _template.md, file-naming, and priority-table layout.

Simple/hub pattern: add track files alongside SKILL.md. Link from a tracks table.

Key constraints:

• References must be one level deep from SKILL.md (no chains)
• Files over 100 lines need a table of contents at the top
• Files are only loaded when explicitly listed in SKILL.md

Advanced options:

• Include executable scripts in scripts/ for Claude to compose — load references/executable-code.md for error handling, constants, plan-validate-execute, runtime environment, package deps, and MCP tool naming
• Add config.json for skills needing user-specific setup context across sessions
• Define on-demand hooks (PreToolUse/PostToolUse) for safety gates or observation

Step 5: Validate

Load references/quality-checklist.md and run all applicable checks.

Step 6: Update README.md

Add a row to the Skills table:

| `<skill-name>` | <phase> | <one-line description> |

Phases used in this repo: Before coding, Project start, Design, Build, Design/dev, Writing/audit, Pre-ship, Pre-merge, Pre-launch, Architecture, Maintenance, Authoring.

Step 7: Smoke-test

Install and confirm files appear in the target directory:

cp -R skills/<name> ~/.claude/skills/
ls ~/.claude/skills/<name>/

Step 8: Evaluate and iterate

Load references/evaluation-and-iteration.md. Define 3+ evaluation scenarios, test on each target model, and iterate based on observed Claude behavior — not assumptions about what Claude should need.

Anti-patterns

• Dumping full specification into SKILL.md body (use reference files)
• Creating reference-to-reference chains (keep one level deep)
• Including time-sensitive content ("before August 2025, use...")
• Restating what Claude already knows (how to write Markdown, general coding advice, standard conventions)
• Using "I audit..." or "Use this to..." voice in descriptions (use third-person)
• Adding README.md, CHANGELOG.md, or INSTALLATION_GUIDE.md to the skill folder
• Dropping files in folders without linking them from SKILL.md
• Over-constraining Claude's approach when specifying outcomes would suffice (railroading)
• Writing the description as a human summary instead of a model trigger with "Use when..." phrases and quoted user phrases
• Skipping a Gotchas section for skills with known failure modes
• Hardcoding absolute paths for persistent data instead of using ${CLAUDE_PLUGIN_DATA}
• Storing persistent data in the skill directory itself (gets deleted on upgrade)
• Referencing MCP tools without the server prefix (bigquery_schema instead of BigQuery:bigquery_schema)
• Magic numbers in scripts with no justifying comment (voodoo constants)
• Shipping a skill without testing it on every target model — what reads well to Opus may underspecify for Haiku

Related Skills

• agents-md for auditing AGENTS.md/CLAUDE.md instruction files
• docs-writing for documentation quality rules