Claude Code Plugins and Marketplace

We’ve seen how to create slash commands, subagents, and skills individually. Plugins allow you to package them together and share them. Today, we explore the Claude Code plugin ecosystem.

What is a Plugin?

A plugin is a pack that can contain:

• Slash commands
• Subagents
• Skills
• Hooks
• MCP servers

All in a standardized structure, easy to install and share.

Installing Plugins

Via the /plugin Command

/plugin install plugin-name

From a Marketplace

/plugin install plugin-name@marketplace-name

From a Git Repo

/plugin install https://github.com/user/plugin-name

From a Local Folder

/plugin install ./my-local-plugin

Managing Installed Plugins

List Plugins

/plugin list

View Plugin Details

/plugin info plugin-name

Remove a Plugin

/plugin remove plugin-name

Plugin Structure

my-plugin/
├── .claude-plugin/
│   ├── plugin.json         # Metadata (required)
│   └── marketplace.json    # For marketplace publishing
├── commands/               # Slash commands
│   ├── review.md
│   └── deploy.md
├── agents/                 # Subagents
│   └── security-expert.md
├── skills/                 # Skills
│   └── api-tester/
│       └── SKILL.md
├── hooks/                  # Hooks
│   └── pre-commit.json
├── .mcp.json              # MCP servers
└── README.md              # Documentation

The plugin.json File

{
  "name": "my-plugin",
  "version": "1.0.0",
  "description": "Description of what the plugin does",
  "author": {
    "name": "Your Name",
    "email": "email@example.com",
    "url": "https://your-site.com"
  },
  "repository": "https://github.com/user/my-plugin",
  "keywords": ["security", "testing", "automation"],
  "license": "MIT",
  "components": {
    "commands": ["commands/"],
    "agents": ["agents/"],
    "skills": ["skills/"],
    "hooks": ["hooks/"],
    "mcpServers": [".mcp.json"]
  }
}

Marketplaces

Concept

A marketplace is a plugin registry, hosted on GitHub or elsewhere.

Adding a Marketplace

/plugin marketplace add owner/repo

Or with a Git URL:

/plugin marketplace add https://gitlab.com/team/plugins.git

Popular Marketplaces

Marketplace Structure

{
  "name": "my-marketplace",
  "owner": {
    "name": "My Team",
    "email": "team@example.com"
  },
  "plugins": [
    {
      "name": "security-suite",
      "source": "./plugins/security-suite",
      "description": "Security tools suite"
    },
    {
      "name": "testing-tools",
      "source": "https://github.com/team/testing-tools",
      "description": "Automated testing tools"
    }
  ]
}

Creating Your First Plugin

Step 1: Create the Structure

mkdir my-first-plugin
cd my-first-plugin
mkdir -p .claude-plugin commands agents skills

Step 2: Create plugin.json

{
  "name": "my-first-plugin",
  "version": "1.0.0",
  "description": "My first Claude Code plugin",
  "author": {
    "name": "Your Name"
  },
  "components": {
    "commands": ["commands/"],
    "agents": ["agents/"]
  }
}

Step 3: Add a Command

<!-- commands/hello.md -->
---
description: Welcome command
---

# /hello

Say hello to the user with their name: $1

Be friendly and offer to help with their project.

Step 4: Add an Agent

<!-- agents/helper.md -->
---
name: helper
description: General development assistant
tools: Read, Grep, Glob
---

You are a friendly and competent development assistant.

## Your Role
Help developers with their technical questions.

## Style
- Concise but complete answers
- Code examples when relevant
- Always propose alternatives

Step 5: Test Locally

/plugin install ./my-first-plugin
/hello Angelo
> @helper How to structure a React project?

Recommended Plugins

For Security

Security Patterns Plugin

• 9 automatic security patterns
• XSS, injection, CSRF detection
• Pre-commit hooks for validation

/plugin install security-patterns

For Testing

Test Generator Plugin

• Automatic test generation
• Vitest, Jest, Mocha support
• Edge case coverage

/plugin install test-generator

For Deployment

Deploy Helper Plugin

• Deployment scripts
• CI/CD integration
• Automatic rollback

/plugin install deploy-helper

For Documentation

Doc Generator Plugin

• Automatic JSDoc
• README generation
• Changelog management

/plugin install doc-generator

Publishing Your Plugin

Option 1: Public GitHub

1. Push your plugin to GitHub
2. Users install with:

   /plugin install https://github.com/you/your-plugin
   

Option 2: Team Marketplace

1. Create a marketplace repo:

{
  "name": "team-plugins",
  "plugins": [
    {
      "name": "your-plugin",
      "source": "./plugins/your-plugin"
    }
  ]
}

1. Share with the team:

   /plugin marketplace add team/team-plugins
   /plugin install your-plugin@team-plugins
   

Option 3: Public Marketplace

Submit your plugin to community marketplaces (see their guidelines).

Plugin Best Practices

1. Clear Documentation

# My Plugin

## Installation
\`\`\`
/plugin install my-plugin
\`\`\`

## Available Commands
- `/command1` - Description
- `/command2` - Description

## Available Agents
- `@agent1` - Description

## Configuration
...

2. Semantic Versioning

{
  "version": "1.2.3"
  // MAJOR.MINOR.PATCH
  // 1 = breaking changes
  // 2 = new features
  // 3 = bug fixes
}

3. Test Your Components

Before publishing:

• Test each command
• Verify agents on multiple cases
• Validate skills activate correctly

4. Minimal Permissions

{
  "components": {
    "agents": [{
      "tools": ["Read", "Grep", "Glob"]
      // No Write or Bash if not needed
    }]
  }
}

Plugins for Teams

Private Marketplace

.claude/settings.json

{
  "extraKnownMarketplaces": {
    "team-internal": {
      "source": {
        "source": "github",
        "repo": "org/internal-plugins"
      }
    }
  }
}

Plugins Shared via Git

Include the plugin in your repo:

project/
├── .claude/
│   └── plugins/
│       └── our-plugin/
└── src/

What’s Coming Tomorrow

In Day 12, we’ll start the integration phase with Hooks: how to automate actions in response to Claude Code events.

This article is part of the “Master Claude Code in 20 Days” series. Day 10: Skills