Microsoft’s official C# SDK for implementing Model Context Protocol (MCP) servers and clients has reached its 1.0 milestone release. The update brings full support for the 2025-11-25 version of the MCP Specification, highlighted by enhanced authorization server discovery and icon metadata for tools, resources, and prompts.
MCP C# SDK 1.0 was unveiled March 5 and can be found on GitHub. The MCP C# SDK 1.0 release represents a major step forward for building MCP servers and clients in .NET, according to Microsoft. Developers can use the SDK to implement secure authorization flows, build rich tool experiences with sampling, or handle long-running operations, the company said.
With authorization server discovery in the 2025-11-25 MCP specification, servers have three ways to expose the Protected Resource Metadata (PRM) document: via a “well-known” URL derived from the server’s MCP endpoint path, at the root well-known URL, and, as before, via a URL in the resource metadata parameter of the WWW-Authentication header.
