MCP Integration for Claude Code Plugins

Overview

Model Context Protocol (MCP) enables Claude Code plugins to integrate with external services and APIs by providing structured tool access. Use MCP integration to expose external service capabilities as tools within Claude Code.

Key capabilities:

• Connect to external services (databases, APIs, file systems)
• Provide 10+ related tools from a single service
• Handle OAuth and complex authentication flows
• Bundle MCP servers with plugins for automatic setup

MCP Server Configuration Methods

Plugins can bundle MCP servers in two ways:

Method 1: Dedicated .mcp.json (Recommended)

Create .mcp.json at plugin root:

{
  "database-tools": {
    "command": "${CLAUDE_PLUGIN_ROOT}/servers/db-server",
    "args": ["--config", "${CLAUDE_PLUGIN_ROOT}/config.json"],
    "env": {
      "DB_URL": "${DB_URL}"
    }
  }
}

Benefits:

• Clear separation of concerns
• Easier to maintain
• Better for multiple servers

Method 2: Inline in plugin.json

Add mcpServers field to plugin.json:

{
  "name": "my-plugin",
  "version": "1.0.0",
  "mcpServers": {
    "plugin-api": {
      "command": "${CLAUDE_PLUGIN_ROOT}/servers/api-server",
      "args": ["--port", "8080"]
    }
  }
}

Benefits:

• Single configuration file
• Good for simple single-server plugins

MCP Server Types

stdio (Local Process)

Execute local MCP servers as child processes. Best for local tools and custom servers.

Configuration:

{
  "filesystem": {
    "command": "npx",
    "args": ["-y", "@modelcontextprotocol/server-filesystem", "/allowed/path"],
    "env": {
      "LOG_LEVEL": "debug"
    }
  }
}

Use cases:

• File system access
• Local database connections
• Custom MCP servers
• NPM-packaged MCP servers

Process management:

• Claude Code spawns and manages the process
• Communicates via stdin/stdout
• Terminates when Claude Code exits

SSE (Server-Sent Events)

Connect to hosted MCP servers with OAuth support. Best for cloud services.

Configuration:

{
  "asana": {
    "type": "sse",
    "url": "https://mcp.asana.com/sse"
  }
}

Use cases:

• Official hosted MCP servers (Asana, GitHub, etc.)
• Cloud services with MCP endpoints
• OAuth-based authentication
• No local installation needed

Authentication:

• OAuth flows handled automatically
• User prompted on first use
• Tokens managed by Claude Code

HTTP (REST API)

Connect to RESTful MCP servers with token authentication.

Configuration:

{
  "api-service": {
    "type": "http",
    "url": "https://api.example.com/mcp",
    "headers": {
      "Authorization": "Bearer ${API_TOKEN}",
      "X-Custom-Header": "value"
    }
  }
}

Use cases:

• REST API-based MCP servers
• Token-based authentication
• Custom API backends
• Stateless interactions

WebSocket (Real-time)

Connect to WebSocket MCP servers for real-time bidirectional communication.

Configuration:

{
  "realtime-service": {
    "type": "ws",
    "url": "wss://mcp.example.com/ws",
    "headers": {
      "Authorization": "Bearer ${TOKEN}"
    }
  }
}

Use cases:

• Real-time data streaming
• Persistent connections
• Push notifications from server
• Low-latency requirements

Environment Variable Expansion

All MCP configurations support environment variable substitution:

${CLAUDE_PLUGIN_ROOT} - Plugin directory (always use for portability):

{
  "command": "${CLAUDE_PLUGIN_ROOT}/servers/my-server"
}

User environment variables - From user's shell:

{
  "env": {
    "API_KEY": "${MY_API_KEY}",
    "DATABASE_URL": "${DB_URL}"
  }
}

Best practice: Document all required environment variables in plugin README.

MCP Tool Naming

When MCP servers provide tools, they're automatically prefixed:

Format: mcp__plugin_<plugin-name>_<server-name>__<tool-name>

Example:

• Plugin: asana
• Server: asana
• Tool: create_task

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