# Module 1: Introduction to Model Context Protocol (MCP)
This module provides a foundational understanding of the Model Context Protocol (MCP), a flexible and extensible architecture designed for seamless communication between LLM applications and integrations.
## Key Concepts Covered
* **Client-Server Architecture**: MCP operates on a client-server model where **Hosts** (LLM applications like Claude Desktop or IDEs) contain **Clients** that establish 1:1 connections with **Servers**. Servers are responsible for providing context, tools, and prompts to clients.
* **Core Components**:
* **Protocol Layer**: Handles high-level communication patterns, message framing, and request/response linking. Key classes include `Protocol`, `Client`, and `Server`.
* **Transport Layer**: Manages the actual communication between clients and servers. All MCP transports utilize **JSON-RPC 2.0** for message exchange.
* **Message Types**: MCP defines four primary JSON-RPC message types:
* **Requests**: Messages that expect a response.
* **Results**: Successful responses to requests.
* **Errors**: Indicate a failed request.
* **Notifications**: One-way messages that do not expect a response.
* **Connection Lifecycle**: An MCP connection follows a clear lifecycle:
* **Initialization**: Client sends an `initialize` request, Server responds, and Client sends an `initialized` notification.
* **Message Exchange**: Normal request-response and notification patterns occur.
* **Termination**: Connections can be closed cleanly or due to disconnections/errors.
* **Transports**: MCP includes built-in transport implementations:
* **Stdio Transport**: Uses standard input/output, ideal for local processes and efficient same-machine communication.
* **HTTP with SSE Transport**: Leverages Server-Sent Events for server-to-client messages and HTTP POST for client-to-server messages, suitable for scenarios requiring HTTP compatibility.
* **Error Handling**: MCP defines standard JSON-RPC error codes and allows for custom application-specific codes. Errors are propagated via error responses, transport error events, and protocol-level handlers.
* **Security and Best Practices**: The module also touches upon crucial aspects like transport security (TLS for remote connections), message validation, resource protection, and robust error management. It emphasizes the importance of logging, diagnostics, and thorough testing for debugging and monitoring MCP implementations.
By understanding these core components and concepts, you are now equipped to grasp how MCP facilitates robust and efficient communication within LLM ecosystems.
