Streamable HTTP

What is Streamable HTTP?

Streamable HTTP is the remote transport for MCP. The client POSTs JSON-RPC messages to one endpoint URL, and the server replies either with a plain JSON response or with a Server-Sent Events stream when it wants to send multiple messages.

One URL is the whole interface. That is what lets an MCP server be a normal web service behind a normal load balancer.

How is it different from the transport it replaced?

The earlier HTTP+SSE transport needed two endpoints: one long-lived SSE connection for server-to-client messages and a separate POST endpoint for client-to-server. Streamable HTTP collapses both into one address.

The practical consequence is deployability. A single POST endpoint survives ordinary infrastructure, whereas a mandatory long-lived connection does not sit well behind serverless platforms or aggressive proxies.

What does this mean for testing a server?

It means a server has an address you can check from anywhere, which a local process does not. Everything we measure depends on that: 53 endpoints attempted between 20 July and 5 August 2026, each one a URL that answered or did not.

Response timings from a check like that measure one round trip from wherever the test ran, not the server's own speed. Across 14 servers on 5 August 2026 the median round trip was around 4.1 seconds and the range ran from 2.7 to 6.4, which says as much about network distance as about the servers.

Example

https://mcp.context7.com/mcp is a complete Streamable HTTP MCP server: one URL, a POST with an initialize body, a revision negotiated in the reply, and tools/list answered over the same address. Anyone can point a client at it without installing anything, which is the difference between a remote server and a stdio one.