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MCP Streaming HTTP Deep Dive
The Model Context Protocol (MCP) standardizes communication between AI clients and servers using HTTP. MCP leverages Streamable HTTP, facilitating both request/response and streaming communication through a single endpoint, usually `/mcp`. Clients initialize a session by POSTing to `/mcp`, exchanging capabilities to establish shared functionality. Clients can then send requests via POST to the same endpoint to execute tasks. Servers respond with either standard JSON responses or streamed Server-Sent Events (SSE) for long operations. SSE allows servers to send incremental updates, indicated by the `Content-Type: text/event-stream` header. Clients can utilize the `sseclient` library to handle the streaming responses. Clients can optionally open an SSE connection using a GET request to the `/mcp` endpoint for continuous updates. Streamable HTTP simplifies the approach compared to legacy models with separate endpoints. The protocol is stateless at the transport level, but session-aware at the protocol level. HTTP is preferred for fast, single responses while SSE is ideal for progress updates and ongoing results. This approach promotes ease of implementation, debugging, and future expansion of the protocol.
