MCP C# SDK 1.0 arrives with improved authorization server discovery

"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."

Microsoft's official C# SDK for Model Context Protocol has achieved its 1.0 milestone release, providing comprehensive support for the 2025-11-25 MCP Specification. The SDK enables developers to implement secure authorization flows, create rich tool experiences with sampling, and manage long-running operations within .NET environments. A key enhancement includes improved authorization server discovery with icon metadata for tools, resources, and prompts. The specification introduces three methods for servers to expose Protected Resource Metadata documents: through a well-known URL derived from the server's MCP endpoint path, at the root well-known URL, or via a URL in the resource metadata parameter of the WWW-Authentication header.

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