plugin-structure

SKILL.md

Plugin Structure for Claude Code

Overview

Claude Code plugins follow a standardized directory structure with automatic component discovery. Understanding this structure enables creating well-organized, maintainable plugins that integrate seamlessly with Claude Code.

Key concepts:

Conventional directory layout for automatic discovery

Manifest-driven configuration in .claude-plugin/plugin.json

Component-based organization (commands, agents, skills, hooks)

Portable path references using ${CLAUDE_PLUGIN_ROOT}

Explicit vs. auto-discovered component loading

Directory Structure

Every Claude Code plugin follows this organizational pattern:
plugin-name/
├── .claude-plugin/
│   └── plugin.json          # Required: Plugin manifest
├── commands/                 # Slash commands (.md files)
├── agents/                   # Subagent definitions (.md files)
├── skills/                   # Agent skills (subdirectories)
│   └── skill-name/
│       └── SKILL.md         # Required for each skill
├── hooks/
│   └── hooks.json           # Event handler configuration
├── .mcp.json                # MCP server definitions
└── scripts/                 # Helper scripts and utilities

Critical rules:

Manifest location: The plugin.json manifest MUST be in .claude-plugin/ directory

Component locations: All component directories (commands, agents, skills, hooks) MUST be at plugin root level, NOT nested inside .claude-plugin/

Optional components: Only create directories for components the plugin actually uses

Naming convention: Use kebab-case for all directory and file names

Plugin Manifest (plugin.json)

The manifest defines plugin metadata and configuration. Located at .claude-plugin/plugin.json:

Required Fields

{
  "name": "plugin-name"
}

Name requirements:

Use kebab-case format (lowercase with hyphens)

Must be unique across installed plugins

No spaces or special characters

Example: code-review-assistant, test-runner, api-docs

Recommended Metadata

{
  "name": "plugin-name",
  "version": "1.0.0",
  "description": "Brief explanation of plugin purpose",
  "author": {
    "name": "Author Name",
    "email": "author@example.com",
    "url": "https://example.com"
  },
  "homepage": "https://docs.example.com",
  "repository": "https://github.com/user/plugin-name",
  "license": "MIT",
  "keywords": ["testing", "automation", "ci-cd"]
}

Version format: Follow semantic versioning (MAJOR.MINOR.PATCH)
Keywords: Use for plugin discovery and categorization

Component Path Configuration

Specify custom paths for components (supplements default directories):

{
  "name": "plugin-name",
  "commands": "./custom-commands",
  "agents": ["./agents", "./specialized-agents"],
  "hooks": "./config/hooks.json",
  "mcpServers": "./.mcp.json"
}

Important: Custom paths supplement defaults—they don't replace them. Components in both default directories and custom paths will load.

Path rules:

Must be relative to plugin root

Must start with ./

Cannot use absolute paths

Support arrays for multiple locations

Component Organization

Commands

Location: commands/ directory
Format: Markdown files with YAML frontmatter
Auto-discovery: All .md files in commands/ load automatically

Example structure:

commands/
├── review.md        # /review command
├── test.md          # /test command
└── deploy.md        # /deploy command

File format:

---
name: command-name
description: Command description
---

Command implementation instructions...

Usage: Commands integrate as native slash commands in Claude Code

Agents

Location: agents/ directory
Format: Markdown files with YAML frontmatter
Auto-discovery: All .md files in agents/ load automatically

Example structure:

agents/
├── code-reviewer.md
├── test-generator.md
└── refactorer.md

File format:

---
description: Agent role and expertise
capabilities:
  - Specific task 1
  - Specific task 2
---

Detailed agent instructions and knowledge...

Usage: Users can invoke agents manually, or Claude Code selects them automatically based on task context

Skills

Location: skills/ directory with subdirectories per skill
Format: Each skill in its own directory with SKILL.md file
Auto-discovery: All SKILL.md files in skill subdirectories load automatically

Example structure:

skills/
├── api-testing/
│   ├── SKILL.md
│   ├── scripts/
│   │   └── test-runner.py
│   └── references/
│       └── api-spec.md
└── database-migrations/
    ├── SKILL.md
    └── examples/
        └── migration-template.sql

SKILL.md format:

---
name: Skill Name
description: When to use this skill
version: 1.0.0
---

Skill instructions and guidance...

Supporting files: Skills can include scripts, references, examples, or assets in subdirectories

Usage: Claude Code autonomously activates skills based on task context matching the description

Hooks

Location: hooks/hooks.json or inline in plugin.json
Format: JSON configuration defining event handlers
Registration: Hooks register automatically when plugin enables

Example structure:

hooks/
├── hooks.json           # Hook configuration
└── scripts/
    ├── validate.sh      # Hook script
    └── check-style.sh   # Hook script

Configuration format:

{
  "PreToolUse": [{
    "matcher": "Write|Edit",
    "hooks": [{
      "type": "command",
      "command": "bash ${CLAUDE_PLUGIN_ROOT}/hooks/scripts/validate.sh",
      "timeout": 30
    }]
  }]
}

Available events: PreToolUse, PostToolUse, Stop, SubagentStop, SessionStart, SessionEnd, UserPromptSubmit, PreCompact, Notification

Usage: Hooks execute automatically in response to Claude Code events

MCP Servers

Location: .mcp.json at plugin root or inline in plugin.json
Format: JSON configuration for MCP server definitions
Auto-start: Servers start automatically when plugin enables

Example format:

{
  "mcpServers": {
    "server-name": {
      "command": "node",
      "args": ["${CLAUDE_PLUGIN_ROOT}/servers/server.js"],
      "env": {
        "API_KEY": "${API_KEY}"
      }
    }
  }
}

Usage: MCP servers integrate seamlessly with Claude Code's tool system

Portable Path References

${CLAUDE_PLUGIN_ROOT}

Use ${CLAUDE_PLUGIN_ROOT} environment variable for all intra-plugin path references:

{
  "command": "bash ${CLAUDE_PLUGIN_ROOT}/scripts/run.sh"
}

Why it matters: Plugins install in different locations depending on:

User installation method (marketplace, local, npm)

Operating system conventions

User preferences

Where to use it:

Hook command paths

MCP server command arguments

Script execution references

Resource file paths

Never use:

Hardcoded absolute paths (/Users/name/plugins/...)

Relative paths from working directory (./scripts/... in commands)

Home directory shortcuts (~/plugins/...)

Path Resolution Rules

In manifest JSON fields (hooks, MCP servers):

"command": "${CLAUDE_PLUGIN_ROOT}/scripts/tool.sh"

In component files (commands, agents, skills):

Reference scripts at: ${CLAUDE_PLUGIN_ROOT}/scripts/helper.py

In executed scripts:

#!/bin/bash
# ${CLAUDE_PLUGIN_ROOT} available as environment variable
source "${CLAUDE_PLUGIN_ROOT}/lib/common.sh"

File Naming Conventions

Component Files

Commands: Use kebab-case .md files

code-review.md → /code-review

run-tests.md → /run-tests

api-docs.md → /api-docs

Agents: Use kebab-case .md files describing role

test-generator.md

code-reviewer.md

performance-analyzer.md

Skills: Use kebab-case directory names

api-testing/

database-migrations/

error-handling/

Supporting Files

Scripts: Use descriptive kebab-case names with appropriate extensions

validate-input.sh

generate-report.py

process-data.js

Documentation: Use kebab-case markdown files

api-reference.md

migration-guide.md

best-practices.md

Configuration: Use standard names

hooks.json

.mcp.json

plugin.json

Auto-Discovery Mechanism

Claude Code automatically discovers and loads components:

Plugin manifest: Reads .claude-plugin/plugin.json when plugin enables

Commands: Scans commands/ directory for .md files

Agents: Scans agents/ directory for .md files

Skills: Scans skills/ for subdirectories containing SKILL.md

Hooks: Loads configuration from hooks/hooks.json or manifest

MCP servers: Loads configuration from .mcp.json or manifest

Discovery timing:

Plugin installation: Components register with Claude Code

Plugin enable: Components become available for use

No restart required: Changes take effect on next Claude Code session

Override behavior: Custom paths in plugin.json supplement (not replace) default directories

Best Practices

Organization

Logical grouping: Group related components together

Put test-related commands, agents, and skills together

Create subdirectories in scripts/ for different purposes

Minimal manifest: Keep plugin.json lean

Only specify custom paths when necessary

Rely on auto-discovery for standard layouts

Use inline configuration only for simple cases

Documentation: Include README files

Plugin root: Overall purpose and usage

Component directories: Specific guidance

Script directories: Usage and requirements

Naming

Consistency: Use consistent naming across components

If command is test-runner, name related agent test-runner-agent

Match skill directory names to their purpose

Clarity: Use descriptive names that indicate purpose

Good: api-integration-testing/, code-quality-checker.md

Avoid: utils/, misc.md, temp.sh

Length: Balance brevity with clarity

Commands: 2-3 words (review-pr, run-ci)

Agents: Describe role clearly (code-reviewer, test-generator)

Skills: Topic-focused (error-handling, api-design)

Portability

Always use ${CLAUDE_PLUGIN_ROOT}: Never hardcode paths

Test on multiple systems: Verify on macOS, Linux, Windows

Document dependencies: List required tools and versions

Avoid system-specific features: Use portable bash/Python constructs

Maintenance

Version consistently: Update version in plugin.json for releases

Deprecate gracefully: Mark old components clearly before removal

Document breaking changes: Note changes affecting existing users

Test thoroughly: Verify all components work after changes

Common Patterns

Minimal Plugin

Single command with no dependencies:

my-plugin/
├── .claude-plugin/
│   └── plugin.json    # Just name field
└── commands/
    └── hello.md       # Single command

Full-Featured Plugin

Complete plugin with all component types:

my-plugin/
├── .claude-plugin/
│   └── plugin.json
├── commands/          # User-facing commands
├── agents/            # Specialized subagents
├── skills/            # Auto-activating skills
├── hooks/             # Event handlers
│   ├── hooks.json
│   └── scripts/
├── .mcp.json          # External integrations
└── scripts/           # Shared utilities

Skill-Focused Plugin

Plugin providing only skills:

my-plugin/
├── .claude-plugin/
│   └── plugin.json
└── skills/
    ├── skill-one/
    │   └── SKILL.md
    └── skill-two/
        └── SKILL.md

Troubleshooting

Component not loading:

Verify file is in correct directory with correct extension

Check YAML frontmatter syntax (commands, agents, skills)

Ensure skill has SKILL.md (not README.md or other name)

Confirm plugin is enabled in Claude Code settings

Path resolution errors:

Replace all hardcoded paths with ${CLAUDE_PLUGIN_ROOT}

Verify paths are relative and start with ./ in manifest

Check that referenced files exist at specified paths

Test with echo $CLAUDE_PLUGIN_ROOT in hook scripts

Auto-discovery not working:

Confirm directories are at plugin root (not in .claude-plugin/)

Check file naming follows conventions (kebab-case, correct extensions)

Verify custom paths in manifest are correct

Restart Claude Code to reload plugin configuration

Conflicts between plugins:

Use unique, descriptive component names

Namespace commands with plugin name if needed

Document potential conflicts in plugin README

Consider command prefixes for related functionality

For detailed examples and advanced patterns, see files in references/ and examples/ directories.