Plugin Structure for Claude Code

Overview

• 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

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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

1. Manifest location: The plugin.json manifest MUST be in .claude-plugin/ directory
2. Component locations: All component directories (commands, agents, skills, hooks) MUST be at plugin root level, NOT nested inside .claude-plugin/
3. Optional components: Only create directories for components the plugin actually uses
4. Naming convention: Use kebab-case for all directory and file names

Plugin Manifest (plugin.json)

Required Fields

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{
  "name": "plugin-name"
}

• 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

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{
  "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"]
}

Component Path Configuration

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

• Must be relative to plugin root
• Must start with ./
• Cannot use absolute paths
• Support arrays for multiple locations

Component Organization

Commands

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commands/
├── review.md        # /review command
├── test.md          # /test command
└── deploy.md        # /deploy command
`**File format**:`
---
name: command-name
description: Command description
---

Command implementation instructions...

Agents

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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...

Skills

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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...

Hooks

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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
    }]
  }]
}

MCP Servers

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

Portable Path References

${CLAUDE_PLUGIN_ROOT}

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

• User installation method (marketplace, local, npm)
• Operating system conventions
• User preferences

• Hook command paths
• MCP server command arguments
• Script execution references
• Resource file paths

• Hardcoded absolute paths (/Users/name/plugins/...)
• Relative paths from working directory (./scripts/... in commands)
• Home directory shortcuts (~/plugins/...)

Path Resolution Rules

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

File Naming Conventions

Component Files

• code-review.md → /code-review
• run-tests.md → /run-tests
• api-docs.md → /api-docs

• test-generator.md
• code-reviewer.md
• performance-analyzer.md

• api-testing/
• database-migrations/
• error-handling/

Supporting Files

• validate-input.sh
• generate-report.py
• process-data.js

• api-reference.md
• migration-guide.md
• best-practices.md

• hooks.json
• .mcp.json
• plugin.json

Auto-Discovery Mechanism

1. Plugin manifest: Reads .claude-plugin/plugin.json when plugin enables
2. Commands: Scans commands/ directory for .md files
3. Agents: Scans agents/ directory for .md files
4. Skills: Scans skills/ for subdirectories containing SKILL.md
5. Hooks: Loads configuration from hooks/hooks.json or manifest
6. MCP servers: Loads configuration from .mcp.json or manifest

• 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

Best Practices

Organization

1. Logical grouping: Group related components together
   • Put test-related commands, agents, and skills together
   • Create subdirectories in scripts/ for different purposes
2. 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
3. Documentation: Include README files
   • Plugin root: Overall purpose and usage
   • Component directories: Specific guidance
   • Script directories: Usage and requirements

Naming

1. Consistency: Use consistent naming across components
   • If command is test-runner, name related agent test-runner-agent
   • Match skill directory names to their purpose
2. Clarity: Use descriptive names that indicate purpose
   • Good: api-integration-testing/, code-quality-checker.md
   • Avoid: utils/, misc.md, temp.sh
3. 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

1. Always use ${CLAUDE_PLUGIN_ROOT}: Never hardcode paths
2. Test on multiple systems: Verify on macOS, Linux, Windows
3. Document dependencies: List required tools and versions
4. Avoid system-specific features: Use portable bash/Python constructs

Maintenance

1. Version consistently: Update version in plugin.json for releases
2. Deprecate gracefully: Mark old components clearly before removal
3. Document breaking changes: Note changes affecting existing users
4. Test thoroughly: Verify all components work after changes

Common Patterns

Minimal Plugin

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

Full-Featured Plugin

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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

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

Troubleshooting

• 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

• 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

• 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

• Use unique, descriptive component names
• Namespace commands with plugin name if needed
• Document potential conflicts in plugin README
• Consider command prefixes for related functionality