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1. What is MCP?2. Core Architecture3. Host vs Client vs Server

Core Architecture

📚 Foundation⏱ 7 min⭐ 50 XP⌨ Hands-on lab

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.
⌨ HANDS-ON LABDiscover Server Capabilities via JSON-RPC
⭐ +125 XP

Discover server capabilities using the 2026-07-28 stateless core protocol over stdio.

1Send a JSON-RPC server/discover request into server-memory stdin.
lab-sandbox — simulated environment
INFINITY LAB SANDBOX v2.6 — simulated shell
Type the command for the current objective. Helpers: "hint", "solution", "clear".
$
OBJECTIVE 1 / 1 — type "hint" if stuck
🧪 Knowledge Check
Press 1-4 to select1 of 3
In MCP architecture, what role does Claude Desktop play?
MCP Server
MCP Host
MCP Transport layer
MCP Proxy