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": "[email protected]",
    "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.

Plugin Structure

Skill Content