Model Context Protocol (MCP) Architecture

The Model Context Protocol (MCP) is an open standard that enables AI applications to connect with external data sources and tools through a unified interface.

Overview

Pattern Description

MCP provides a standardized way for AI applications (hosts) to communicate with external systems (servers) using a client-server architecture with JSON-RPC 2.0 messaging.

Components

MCP Host

• Purpose: The AI application that needs external capabilities
• Examples: Claude Desktop, IDEs, custom AI applications
• Contains: MCP Client for managing server connections

MCP Client

• Purpose: Manages connections to MCP servers
• Key Responsibilities:
  • Server discovery and connection
  • Capability negotiation
  • Request routing and response handling
  • Connection lifecycle management

MCP Server

• Purpose: Exposes capabilities to AI applications
• Primitives Provided:
  • Tools: Executable functions the AI can invoke
  • Resources: Data and context the AI can read
  • Prompts: Reusable prompt templates

Communication Protocol

Server Examples

File System Server

{
  "tools": [
    {
      "name": "read_file",
      "description": "Read contents of a file",
      "inputSchema": {
        "type": "object",
        "properties": {
          "path": { "type": "string" }
        }
      }
    }
  ]
}

Database Server

{
  "tools": [
    {
      "name": "query",
      "description": "Execute SQL query",
      "inputSchema": {
        "type": "object",
        "properties": {
          "sql": { "type": "string" }
        }
      }
    }
  ],
  "resources": [
    {
      "uri": "db://schema",
      "name": "Database Schema",
      "mimeType": "application/json"
    }
  ]
}

When to Use

• Building AI applications that need external data access
• Creating reusable tool integrations across multiple AI hosts
• Standardizing how AI connects to enterprise systems
• Developing IDE extensions with AI capabilities
• Building composable AI agent architectures

Benefits

Related Patterns

Resources

• MCP Specification
• MCP SDKs