Streamable HTTP

Streamable HTTP is the HTTP transport for remote MCP servers: a single endpoint that takes each JSON-RPC message as a POST and answers with either a JSON object or an SSE stream.

Streamable HTTP arrived with protocol revision 2025-03-26 and replaces the older HTTP plus SSE transport from 2024-11-05. Per request, the server decides whether a single response is enough or whether it streams progress notifications over Server-Sent Events before the final result. Revision 2026-07-28 tightens the model further: protocol level sessions and the standalone GET stream are gone, and routing metadata moves into the Mcp-Method and Mcp-Name headers. A server can then sit behind an ordinary load balancer, with no sticky sessions and no gateway unpacking the request body.

Related terms

Model Context Protocol (MCP)The Model Context Protocol (MCP) is an open standard for connecting AI applications to external tools and data through one shared interface instead of one custom integration per system.MCP ServerAn MCP server is the far side of the Model Context Protocol: the program that offers an AI client a defined set of tools, resources and prompts.Tool CallA tool call is a model's structured request to run exactly one named function with validated arguments. Execution happens outside the model.

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