| name | mcp-fundamentals |
| description | core architecture of the Model Context Protocol (MCP). Use this to understand Hosts, Clients, Servers, and the JSON-RPC communication layer. |
MCP Fundamentals
Goal
Understand the Model Context Protocol (MCP) architecture to solve the "$N \times M$" integration problem, decoupling AI models from the specific implementation details of external tools.
Core Architectural Components
1. The Host (The Application)
- Definition: The container application (e.g., a desktop app, IDE, or agent platform) that manages the user experience and orchestrates tool usage.
- Responsibilities:
- Creating and managing MCP clients.
- Enforcing security policies and content guardrails.
- Managing the user interaction lifecycle.
2. The Client (The Connector)
- Definition: A software component embedded within the Host that maintains a 1:1 connection with a specific Server.
- Responsibilities:
- Issuing commands to the server.
- Receiving and processing responses or notifications.
- Managing the session lifecycle.
3. The Server (The Provider)
- Definition: A standalone program that exposes capabilities (Tools, Resources, Prompts) to the AI application.
- Responsibilities:
- Tool Discovery: Advertising what tools are available.
- Execution: Receiving commands and running the actual logic/API calls.
- Formatting: Returning standardized results to the client.
The Communication Layer
Protocol: JSON-RPC 2.0
All communication is text-based and language-agnostic, relying on four standard message types:
- Requests: Calls expecting a response (e.g.,
tools/call).
- Results: Successful responses containing data.
- Errors: Failure messages with codes and descriptions.
- Notifications: One-way messages requiring no response (e.g., logging).
Transport Mechanisms
- stdio (Standard Input/Output):
- Use Case: Local, private tools.
- Mechanism: The Host spawns the Server as a subprocess and communicates via standard I/O pipes. Best for accessing local files or scripts.
- Streamable HTTP (SSE):
- Use Case: Remote or distributed tools.
- Mechanism: Uses Server-Sent Events (SSE) for streaming responses, allowing connections to remote services over standard HTTP.
