Streamable HTTP

Act Streamable HTTP is the primary remote transport for the Model Context Protocol (MCP), replacing the early dual-endpoint HTTP+SSE transport from the 2024-11-05 specification. Under Streamable HTTP, an MCP server exposes a single HTTP endpoint (commonly /mcp) that accepts JSON-RPC 2.0 POST requests and can respond either with a single application/json body or an upgraded text/event-stream (SSE) stream when streaming notifications or progress. As of the 2026-07-28 MCP release, Streamable HTTP operates statelessly by default using MCP-Protocol-Version, Mcp-Method, and Mcp-Name headers without requiring a sticky session handshake. Used by: mcp.