Create Skill

Skills are modular, filesystem-based capabilities that provide domain expertise on demand. This skill teaches how to create effective skills.

1. Skills Are Prompts

All prompting best practices apply. Be clear, be direct, use XML structure. Assume Claude is smart - only add context Claude doesn't have.

2. SKILL.md Is Always Loaded

When a skill is invoked, Claude reads SKILL.md. Use this guarantee:

• Essential principles go in SKILL.md (can't be skipped)
• Workflow-specific content goes in workflows/
• Reusable knowledge goes in references/

3. Router Pattern for Complex Skills

skill-name/
├── SKILL.md              # Router + principles
├── workflows/            # Step-by-step procedures (FOLLOW)
├── references/           # Domain knowledge (READ)
├── templates/            # Output structures (COPY + FILL)
└── scripts/              # Reusable code (EXECUTE)

SKILL.md asks "what do you want to do?" → routes to workflow → workflow specifies which references to read.

When to use each folder:

• workflows/ - Multi-step procedures Claude follows
• references/ - Domain knowledge Claude reads for context
• templates/ - Consistent output structures Claude copies and fills (plans, specs, configs)
• scripts/ - Executable code Claude runs as-is (deploy, setup, API calls)

4. Pure XML Structure

No markdown headings (#, ##, ###) in skill body. Use semantic XML tags:

<objective>...</objective>
<process>...</process>
<success_criteria>...</success_criteria>

Keep markdown formatting within content (bold, lists, code blocks).

5. Progressive Disclosure

SKILL.md under 500 lines. Split detailed content into reference files. Load only what's needed for the current workflow.

Based on the user's message, route directly to the appropriate workflow:

Creating new skills:

• Domain expertise (exhaustive knowledge base) → Use create-domain-expertise skill instead (separate skill with batched subagent orchestration)
• Task-execution skill (does specific things) → workflows/create-new-skill.md

Working with existing skills:

• Audit, review, check → workflows/audit-skill.md
• Verify content is current → workflows/verify-skill.md
• Add workflow → workflows/add-workflow.md
• Add reference → workflows/add-reference.md
• Add template → workflows/add-template.md
• Add script → workflows/add-script.md
• Upgrade to router pattern → workflows/upgrade-to-router.md

Need help deciding:

• General guidance → workflows/get-guidance.md

If user intent is unclear, ask minimal clarifying questions:

• "Create a MIDI skill" → "Task-execution skill (does MIDI tasks) or domain expertise (complete MIDI knowledge base)?"
• "Work on my skill" → "Which skill? What do you want to do with it?"
• Ask one clarifying question round at a time, then wait for the user's actual response before asking another.
• Never fabricate or simulate user responses while clarifying (for example, fake [User] markers or imagined answers).

Then proceed directly to the workflow.

Skill directories:

• Bundled/read-only: ~/.gsd/agent/skills/{skill-name}/
• Global: ~/.agents/skills/{skill-name}/
• Project-local: .agents/skills/{skill-name}/

User-authored skills should target the global or project-local directories; GSD manages the bundled directory during install/update.

Simple skill (single file):

---
name: skill-name
description: What it does and when to use it.
---

<objective>What this skill does</objective>
<quick_start>Immediate actionable guidance</quick_start>
<process>Step-by-step procedure</process>
<success_criteria>How to know it worked</success_criteria>

Complex skill (router pattern):

SKILL.md:
  <essential_principles> - Always applies
  <intake> - Question to ask
  <routing> - Maps answers to workflows

workflows/:
  <required_reading> - Which refs to load
  <process> - Steps
  <success_criteria> - Done when...

references/:
  Domain knowledge, patterns, examples

templates/:
  Output structures Claude copies and fills
  (plans, specs, configs, documents)

scripts/:
  Executable code Claude runs as-is
  (deploy, setup, API calls, data processing)

All in references/:

Structure: recommended-structure.md, skill-structure.md Principles: core-principles.md, be-clear-and-direct.md, use-xml-tags.md Patterns: common-patterns.md, workflows-and-validation.md Assets: using-templates.md, using-scripts.md Advanced: executable-code.md, api-security.md, iteration-and-testing.md GSD-specific: gsd-skill-ecosystem.md

All in workflows/:

Required fields:

---
name: skill-name          # lowercase-with-hyphens, matches directory
description: ...          # What it does AND when to use it (third person)
---

Frontmatter must parse as YAML. Quote description values containing : or use a folded block (description: >) for longer trigger descriptions.

Name conventions: create-*, manage-*, setup-*, generate-*, build-*