Building integrations for Large Language Models often requires creating custom connectors for every distinct data source. The Model Context Protocol (MCP) addresses this fragmentation by providing a standardized open protocol. It decouples the data provider from the client application, allowing a single server to expose resources to any MCP-compliant client.

This chapter establishes the technical baseline required to construct these integrations. We focus on the architectural definitions rather than immediate code implementation. You will examine the Client-Host-Server topology to understand how responsibility is distributed across the system. We also analyze the communication layer, which relies on JSON-RPC 2.0 messages to handle requests, responses, and notifications.

The protocol supports specific transport mechanisms depending on whether the connection is local or remote. We will compare standard input/output (stdio) for local process communication against Server-Sent Events (SSE) for HTTP-based connections. Understanding these transport layers is necessary for debugging connection issues later.

By the end of this chapter, you will be able to:

• Define the roles and responsibilities of MCP Clients, Hosts, and Servers.
• Analyze the structure of JSON-RPC messages used in the protocol.
• Select the appropriate transport mechanism for your specific use case.
• Explain the capabilities negotiation process during the initialization handshake.
• Configure a local development environment with the necessary SDKs.