plugin-structure

Plugin Structure for Claude Code

Overview

Claude Code plugins follow a standardized directory structure with automatic component discovery. Master this structure to create 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:

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)

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

Simple, user-invocable prompts stored as single .md files. Use when you don't need bundled resources. Both commands and skills are invoked via the Skill tool—commands are essentially simple skills.

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

Complex prompts with bundled resources (scripts, references, examples). Use when you need progressive disclosure or supporting files. Both skills and commands are invoked via the Skill tool.

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
---

Skill instructions and guidance...

Tool restrictions (optional): Skills can include allowed-tools in frontmatter to limit tool access:

---
name: safe-reader
description: Read-only file access skill
allowed-tools: Read, Grep, Glob # Optional: restricts available tools
---

Use for read-only workflows, security-sensitive tasks, or limited-scope operations.

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:

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

Available events: PreToolUse, PermissionRequest, 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

LSP Servers

Location: Inline in plugin.json under lspServers field Format: JSON configuration for Language Server Protocol servers Auto-start: Servers start when files matching extensions are opened

Example format:

{
  "lspServers": {
    "python": {
      "command": "pyright-langserver",
      "args": ["--stdio"],
      "extensionToLanguage": {
        ".py": "python",
        ".pyi": "python"
      }
    }
  }
}

Usage: LSP servers provide code intelligence (go-to-definition, find references, hover)

For detailed LSP configuration, see the lsp-integration skill.

Output Styles

Location: Path reference in plugin.json under outputStyles field Format: String path or array of paths to style files/directories Purpose: Customize how Claude formats responses

Example format:

{
  "outputStyles": "./styles/"
}

Or with multiple paths:

{
  "outputStyles": ["./styles/default.md", "./styles/compact.md"]
}

Usage: Plugins can define consistent output formatting for their domain. Style files in the referenced path are loaded to customize Claude's output behavior.

For comprehensive output styles guidance including frontmatter schema, file locations, and when to use styles vs other components, see references/output-styles.md.

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:

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

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

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

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

Plugin Caching

Claude Code caches plugin content for performance. Understanding caching behavior helps with development and debugging.

What Gets Cached

• Plugin manifest (plugin.json)
• Component files (commands, agents, skills)
• Configuration files (hooks.json, .mcp.json)

Cache Invalidation

Cached content refreshes when:

• Claude Code session restarts
• Plugin is reinstalled or updated
• User runs /plugins refresh (if available)

Why External Paths Fail

Important: Paths outside the plugin directory may not work reliably because:

1. Security boundary - Plugins are sandboxed to their directory
2. Caching - External paths aren't monitored for changes
3. Portability - External paths break on different machines

Always use:

• ${CLAUDE_PLUGIN_ROOT} for paths within the plugin
• Bundled resources instead of external file references
• Environment variables for user-specific paths

Development Workflow

During development, reload plugins by:

1. Exiting Claude Code
2. Making changes to plugin files
3. Restarting Claude Code

Or use --plugin-dir for testing without installation:

claude --plugin-dir /path/to/plugin

Runtime Contexts

Plugins behave differently depending on the runtime context. Interactive sessions support slash commands and user prompts; headless mode (claude -p) and GitHub Actions provide non-interactive environments where some features are unavailable.

• Headless/CI mode: See references/headless-ci-mode.md for designing plugins that work in claude -p and CI pipelines
• GitHub Actions: See references/github-actions.md for integrating plugins with claude-code-action@v1
• Advanced topics: See references/advanced-topics.md for caching behavior, installation scopes, CLI management, keybindings, status line, and auto-update behavior

Plugin Validation

Claude Code provides built-in validation tools:

• claude plugin validate (CLI) / /plugin validate (TUI): Validates plugin and marketplace structure, checking JSON syntax, required fields, component discovery, and path resolution
• claude --debug: Shows detailed plugin loading logs, including which components were discovered, registration errors, and hook execution details
• claude --verbose: Use --verbose for additional debugging output during plugin loading, including hook registration and MCP server connections
• /plugins: View installed plugins, their status, and any errors in the Errors tab

Use validation early and often during development.

Additional Source Types

Beyond relative paths and git sources, plugins can also be installed from:

• npm: claude plugin install npm-package-name
• pip: claude plugin install pip-package-name

These package managers handle versioning and dependency resolution automatically.

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

---

Additional Resources

Reference Files

• references/component-patterns.md - Detailed patterns for each component type
• references/manifest-reference.md - Complete plugin.json field reference
• references/headless-ci-mode.md - Headless and CI mode plugin compatibility
• references/github-actions.md - GitHub Actions integration for plugins
• references/advanced-topics.md - Caching, installation scopes, CLI commands, and more
• references/output-styles.md - Output style frontmatter schema, file locations, and usage guidance

Example Files

Working examples in examples/:

• minimal-plugin.md - Single command plugin structure
• standard-plugin.md - Typical plugin with multiple components
• advanced-plugin.md - Full-featured plugin with all component types