Skill Structure

Commands and Skills Are Merged

Custom slash commands and skills are the same thing. A file at .claude/commands/review.md and a skill at .claude/skills/review/SKILL.md both create /review. Existing .claude/commands/ files keep working. Skills add: a directory for supporting files, frontmatter to control invocation, and automatic context loading.

If a skill and command share the same name, the skill takes precedence.

When to use which:

Type	When
Command file (commands/name.md)	Simple single-file workflow, no supporting files
Skill directory (skills/name/SKILL.md)	Needs references, background knowledge, or progressive disclosure

Naming Rules

Rule	Example
Format	kebab-case, lowercase, 1-64 chars
Pattern	^[a-z][a-z0-9]*(-[a-z0-9]+)*$
Must match	Directory name exactly

Good/Bad Examples:

Good	Bad	Why
stimulus-coder	MySkill	Uppercase not allowed
tdd-workflow	skill_helper	Underscores not allowed
pdf-processing	-invalid	Can't start with hyphen
seo-content	skill--bad	No consecutive hyphens

Directory Structure

Flat Structure (most skills)

plugins/majestic-rails/skills/stimulus-coder/SKILL.md
-> name: stimulus-coder
-> invoked as: Skill("stimulus-coder")

Nested Structure (categorized skills)

plugins/majestic-rails/skills/dhh-coder/SKILL.md
-> name: dhh-coder
-> invoked as: Skill("dhh-coder")

Key Points:

• The name field is ONLY the final skill name (not the full path)
• Directory name must match name exactly
• Use nesting to group related skills (ceo/, fundraising/, research/)

Progressive Disclosure

For complex skills, split into multiple files:

my-skill/
+-- SKILL.md (overview, <500 lines)
+-- references/
|   +-- patterns.md (detailed patterns)
|   +-- examples.md (extended examples)
+-- scripts/
    +-- helper.py (utility scripts)

Rules:

• References one level deep only (SKILL.md to reference.md, not deeper)
• Scripts execute without loading into context
• Keep SKILL.md focused on navigation and core content
• Subdirectories only: scripts/, references/, assets/

Frontmatter

Core Fields

---
name: skill-name              # Matches directory, defaults to dir name if omitted
description: What it does...  # Recommended, max 1024 chars
allowed-tools: Read Bash      # Optional, space-delimited
---

All Fields Reference

Field	Required	Description
name	No	Lowercase letters, numbers, hyphens (max 64 chars). Defaults to directory name.
description	Recommended	What it does AND when to use it. Max 1024 chars.
argument-hint	No	Hint during autocomplete. Example: [issue-number]
disable-model-invocation	No	true = Claude cannot auto-load. For manual workflows. Default: false
user-invocable	No	false = hidden from / menu. For background knowledge. Default: true
allowed-tools	No	Tools without permission prompts. Example: Read, Bash(git *)
model	No	haiku, sonnet, or opus
context	No	fork to run in isolated subagent context
agent	No	Subagent type when context: fork: Explore, Plan, general-purpose, or custom

Description Template

[What it does]. Use when [trigger contexts]. Triggers on [specific keywords].

Rules:

• Max 1024 characters
• Third person ("Processes..." not "I process...")
• Include trigger keywords users would naturally say

Invocation Control

Frontmatter	User can invoke	Claude can invoke	When loaded
(default)	Yes	Yes	Description always in context, full content on invocation
user-invocable: false	No	Yes	Description always in context, loads when relevant

Decision guide:

• Background knowledge (conventions, domain context) -> user-invocable: false
• Everything else -> defaults (both user and model can invoke)

Note: Avoid disable-model-invocation: true. Commands/skills with side effects should use confirmation steps (AskUserQuestion) rather than blocking model invocation entirely.

Dynamic Features

Arguments

Use $ARGUMENTS for user input. If not present in content, arguments are appended automatically.

---
name: fix-issue
---
Fix GitHub issue $ARGUMENTS following our coding standards.

Individual args: $ARGUMENTS[0] or shorthand $0, $1, $2.

Dynamic Context Injection

The !`command` syntax runs shell commands before content reaches Claude:

## Context
- Current branch: !`git branch --show-current`
- PR diff: !`gh pr diff`

Commands execute immediately; output replaces the placeholder.

Subagent Execution

Add context: fork to run in isolation (no conversation history):

---
name: deep-research
description: Research a topic thoroughly
context: fork
agent: Explore
---
Research $ARGUMENTS thoroughly...

Tool Access

Tools Needed	Example Use Case
Read, Grep, Glob	Search codebase for patterns
Bash(git *)	Git operations only
Bash(gh *)	GitHub CLI operations
WebFetch	Fetch external documentation
None	Pure knowledge/guidance

Limits

• SKILL.md: Max 500 lines
• Name: Max 64 characters
• Description: Max 1024 characters

Validation Checklist

• Name matches directory name exactly
• Name follows pattern ^[a-z][a-z0-9]*(-[a-z0-9]+)*$
• Description under 1024 chars with trigger keywords
• Uses standard markdown headings (not XML tags)
• SKILL.md under 500 lines
• Uses AskUserQuestion for confirmation if skill has side effects
• allowed-tools set if specific tools needed
• No persona statements or attribution
• Subdirectories only: scripts/, references/, assets/
• Tested with real usage