agent-skills-creator

name

agent-skills-creator

description

Guides creation of best-practice agent skills following the open format specification. Covers frontmatter, directory structure, progressive disclosure, reference files, rules folders, degrees of freedom, content patterns, executable scripts, MCP tool references, evaluations, and cross-model testing. Use when creating a new skill, authoring SKILL.md, setting up a rules-based audit skill, structuring a skill bundle, writing scripts inside a skill, evaluating a skill, or asking "how to write a skill."

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

File	Read When
references/format-specification.md	Default: frontmatter constraints, directory structure, naming rules, advanced features
references/skill-categories.md	Choosing what type of skill to build (Step 1)
references/skill-patterns.md	Choosing a structural pattern or need a template for a specific skill type
references/authoring-tips.md	Writing high-signal content, degrees of freedom, content patterns, setup, storage, hooks
references/executable-code.md	Skill includes scripts, depends on packages, or invokes MCP tools
references/rules-folder-structure.md	Building a rules-based audit/lint skill with categorized rule files
references/evaluation-and-iteration.md	Designing evaluations, testing across models, iterating on a shipped skill
references/quality-checklist.md	Final validation before shipping

Choose a Skill Category

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

Category	What it solves	Common pattern
Library & API Reference	How to use a library/CLI/SDK correctly	Simple/hub
Product Verification	Test/verify with tools (Playwright, tmux)	Workflow
Data Fetching & Analysis	Connect to data/monitoring stacks	Workflow, Mixed
Business Process Automation	Automate repetitive team workflows	Workflow
Code Scaffolding & Templates	Generate boilerplate and project structure	Workflow
Code Quality & Review	Enforce code quality standards	Rules-based, Workflow
CI/CD & Deployment	Fetch, push, deploy code	Workflow
Runbooks	Symptom to investigation to structured report	Workflow, Mixed
Infrastructure Operations	Maintenance with guardrails	Workflow

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

Choose a Skill Pattern

Pattern	When to use	Example	Key files
Simple/hub	Dispatch to 2-5 focused files by track	ui-design	SKILL.md + track files
Workflow	Multi-step process with progressive loading	agents-md, review-pr	SKILL.md + references/
Rules-based	Audit/lint with categorized rules	typography-audit, docs-writing	SKILL.md + rules/
Mixed	Workflow with conditional references	multi-tenant-architecture	SKILL.md + references/

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