The Three Main Pillars

MCP architecture consists of three logical components:

1. MCP Hosts: The application the user interacts with (e.g., Claude Desktop, Cursor). It bridges the gap between the LLM and the protocol.
2. MCP Clients: The protocol implementation running inside the Host. It initiates the connection to servers.
3. MCP Servers: Lightweight, independent programs that expose specific data (Resources), actions (Tools), or templates (Prompts).

A Typical Request Flow

When you ask "Summarize my recent GitHub PRs":

1. Claude Desktop (Host) connects to your GitHub MCP Server via local stdio.
2. The Host asks the Server: "What capabilities do you offer?"
3. The Server replies: "I have tools: get_prs, read_file, and search_repo."
4. The LLM decides to use get_prs. The Host sends the execution request to the Server.
5. The Server executes the API call securely and returns the JSON data to the Host to display.