Table of Contents
1. The Three Core Concepts of MCP Architecture

stack:
- MCP Host (The Application): This is the overall software framework, such as Claude Desktop, which runs the AI agent framework and orchestrates tool use.
- MCP Client (The Plugin): This acts as a gateway within the host application, managing the direct connection to specific external capabilities.
- MCP Server (The Capability Provider): This is the external code that actually executes the tools, manages data lookups (context), or supplies prompt templates to the agent.
2. Practical Example: ‘Fetch’ MCP Server
This flowchart shows the live process of the hypothetical ‘Fetch’ server handling a request:
- It demonstrates how a user prompt triggers the MCP Client in Claude Desktop.
- The system then connects to the local Fetch Server, which uses Playwright to drive a headless Chrome browser behind the scenes.
- Finally, the raw web content is returned to Claude to provide the user with a response based on real-time internet data.