MCP Client Architecture

Model Context Protocol (MCP) client architecture defines how host applications, such as IDE agents, CLI tools, and custom agents, implement the client side of MCP: discovering servers, negotiating capabilities, managing connections, routing tool calls, and handling session lifecycle. The client is the trust boundary in the MCP ecosystem, deciding which tool call requests from the model to execute, which servers to connect to, and what permissions to grant, making client design the primary security control point. Most developers interact with MCP through existing clients like Claude Desktop or Cursor, but building a custom client unlocks the ability to create specialized agent systems that compose MCP servers in novel ways.