Microsoft has released (MCP) servers and clients.
Unveiled , which Microsoft described as the protocol’s largest revision since its launch. The 2026-07-28 revision makes the MCP protocol stateless by default, standardizes the HTTP surface to allow ordinary HTTP infrastructure to route MCP traffic, and introduces Multi Round-Trip Requests (MRTR) to support interaction without requiring long-lived sessions.
MCP C# SDK 2.0 moves in lockstep with these changes, Microsoft said. The HTTP server transport now runs statelessly by default. Whereas version 1.x of the SDK configured stateful sessions out of the box, in version 2.0 HttpServerTransportOptions.Stateless defaults to true.
MCP C# SDK v2.0 also implements a small set of HTTP headers that the 2026-07-28 MCP revision standardizes. A tools/call now includes Mcp-Method: tools/call and Mcp-Name: get_order_status alongside the JSON-RPC body. With the 2026-07-28 revision, an MCP request becomes a single, self-describing HTTP POST. This means that ordinary HTTP infrastructure such as load balancers, proxies, gateways, and web application firewalls now can act on MCP traffic without deep packet inspection, Microsoft said.
And MCP C# SDK 2.0 adds support for MRTR on the server and on the client. MRTR addresses scenarios in which tools can’t answer in a single round trip, such as when a server wants to confirm with a user before taking a significant action. In previous versions of MCP, these interactions worked only over a live, stateful session. With MRTR, they work with no session at all, because all the continuity travels in the payload, Microsoft said.
With the 2026-07-28 spec compliance landing in MCP C# SDK 2.0, Microsoft said the SDK’s next focus is end-to-end authentication and authorization. The goal is to make secure MCP deployments as “turnkey” as the rest of the stack, building on the closer OAuth and OpenID Connect alignment the spec introduced, Microsoft said.
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