create-skill

Creating Skills

Process

1. Gather requirements — ask the user (use AskUserQuestion when available; otherwise present numbered options):
   • What task or domain does the skill cover?
   • What specific use cases should it handle?
   • Does it need executable scripts, or just instructions?
   • Any reference material to include?
2. Explore existing skills — ls skills/ and read 1–2 neighbors to match conventions.
3. Draft — create SKILL.md; split deep material into references/ if it exceeds ~150 lines; add scripts/ only for deterministic helpers.
4. Review with user — present the draft and ask:
   • Does this cover your use cases?
   • Anything missing or unclear?
   • Should any section be more or less detailed?

Skill Structure

skill-name/
├── SKILL.md              # Required. Metadata + instructions.
├── references/           # Optional. Long-form docs the agent reads on demand.
│   └── <topic>.md
├── scripts/              # Optional. Deterministic helpers (.sh, .py) called via Bash.
│   └── helper.sh
└── assets/               # Optional. Files used in output (templates, icons, fonts).
    └── template.md

Keep the entry point in SKILL.md. Link from SKILL.md to references/<topic>.md rather than inlining — preserves progressive disclosure.

Progressive disclosure (three levels)

1. Metadata (name + description) — always in context (~100 words). Sole signal for triggering.
2. SKILL.md body — loaded when skill triggers. Keep under ~150 lines; the spec ceiling is ~500.
3. Bundled resources (references/, scripts/, assets/) — loaded on demand or executed without loading.

SKILL.md Template

---
name: skill-name
description: One sentence what it does. Use when [triggers]. Don't use when [anti-triggers].
---

# Skill Name

## Workflow
[numbered steps]

## Rules
[hard constraints]

## Error Handling
[if X — do Y]

Orchestrator skills (e.g. review, ship) replace Workflow with explicit phases that announce each sub-skill being invoked.

Frontmatter Fields

Field	Required	Notes
name	yes	kebab-case, matches directory. Avoid version suffixes (-v2, -new) — evolve in place or deprecate
description	yes	Agent's only signal for when to load this skill
argument-hint	no	One-line hint shown next to the skill name (e.g. '[slug]', '<idea>')

Avoid compatibility: and allowed-tools: — legacy npx skills CLI fields, not part of the Claude Code plugin spec.

Description Requirements

The description is the only thing the agent sees when deciding which skill to load. It's surfaced in the system prompt alongside every other installed skill — the agent reads descriptions and picks one based on the user's request.

Goal: give the agent just enough to know

1. What capability the skill provides
2. When and why to trigger it (keywords, contexts, file types)
3. When NOT to use it (anti-triggers that point at neighbor skills)

Format:

• Max 1024 chars
• Third person
• First sentence: what it does
• Second sentence: Use when [triggers]
• Third sentence: Don't use for [anti-triggers]

Combat under-triggering: Claude tends to under-trigger skills. If a skill is useful but rarely fires, make the description more assertive — list extra phrases the user might say, name file types or contexts explicitly, even add Make sure to use this skill whenever... when warranted. Anti-triggers stay important, but the trigger clause should be generous.

Good:

Extract text and tables from PDF files, fill forms, merge documents. Use when working with PDF files or when user mentions PDFs, forms, or document extraction. Don't use for image OCR (use vision skill) or DOCX files.

Bad:

Helps with documents.

The bad example gives the agent no way to distinguish this from any other document skill.

When to Add Scripts

Add scripts/ helpers when:

• The operation is deterministic (validation, scanning, formatting)
• The same logic would otherwise be regenerated on every invocation
• Errors need explicit handling and predictable exit codes

Scripts save tokens and improve reliability vs. ad-hoc generated code.

When to Split Files

Split into references/<topic>.md when:

• SKILL.md exceeds ~150 lines
• Content has distinct domains (e.g. patterns vs. report template)
• Advanced material is rarely needed during the main workflow

Domain organization: when a skill supports multiple variants, split by variant so the agent loads only the relevant one:

cloud-deploy/
├── SKILL.md              # workflow + variant selection
└── references/
    ├── aws.md
    ├── gcp.md
    └── azure.md

Writing Style

• Imperative form for instructions (Run X, Check Y — not You should run X)
• Explain the why instead of stacking ALWAYS/NEVER in caps. Today's models have theory of mind; reasoning lands better than rigid rules
• A single MUST is fine when a hard constraint exists; a wall of caps is a yellow flag — reframe and explain

Pre-loaded Context

Workflow skills can pre-load shell output via the ! prefix:

## Pre-loaded context

- Status: !`git status`
- Diff: !`git diff HEAD`

The harness executes each command and injects its output as context. Use for state the skill always needs — git status, package.json, file listings.

Review Checklist

Before shipping a new or modified skill:

• Folder name matches name: field
• Description has three sentences (what, when, when-not)
• Body has Workflow + Rules + Error Handling sections
• SKILL.md under ~150 lines (split into references/ if longer)
• Concrete examples included
• No time-sensitive info (versions, dates)
• No compatibility: or allowed-tools: legacy fields
• Cross-refs to neighbor skills use relative paths (e.g. [validate-code](../validate-code/SKILL.md))
• Added to README skills table under the correct phase
• Added to AGENTS.md intent → skill mapping
• No existing skill already covers this use case

Anti-patterns

• Description without triggers: "Helps with testing." — useless
• Hardcoded versions or dates that go stale
• No error handling for skills that run Bash commands
• Inlining 200+ lines of reference material instead of splitting into references/