MCP C# SDK

license

Apache-2.0(OSI

source

public(the SDK and its documentation)

self-host

yes(a library you build against)

core features withheld

no — nothing withheld from the published tree

Open source under the Model Context Protocol project's dual transition licence: Apache-2.0 for new contributions, MIT retained where authors have not consented to relicensing. The classifier reports NOASSERTION over it, which is the file's shape rather than the grant, and the body is cited.

• https://api.github.com/repos/modelcontextprotocol/csharp-sdk recorded 2026-09-17

  Repository metadata: 4,532 stars, not archived, not a fork, last pushed 2026-09-14, description "The official C# SDK for Model Context Protocol servers and clients. Maintained in collaboration with Microsoft."

• https://raw.githubusercontent.com/modelcontextprotocol/csharp-sdk/main/LICENSE recorded 2026-09-17

  The LICENSE body, read rather than the classifier's label. It opens "The MCP project is undergoing a licensing transition from the MIT License to the Apache License, Version 2.0", licensing new contributions Apache-2.0 and retaining MIT where relicensing consent was not given. That preamble is what GitHub's classifier cannot match, and it is why the API reports NOASSERTION.

NuGet reports downloads for `ModelContextProtocol` as a cumulative all-time total rather than a figure for a single month, so it cannot be compared against the monthly download counts other packages report. GitHub stars are the only remaining signal, and a star count is not a count of use.

• https://api.github.com/repos/modelcontextprotocol/csharp-sdk recorded 2026-09-17

  Repository metadata for modelcontextprotocol/csharp-sdk: 4,532 stargazers.

• https://azuresearch-usnc.nuget.org/query?q=packageid:ModelContextProtocol&prerelease=true recorded 2026-09-17

  NuGet search API for packageid:ModelContextProtocol: version 2.2.0, totalDownloads 31,852,326 - a cumulative figure, recorded here as context for the abstention from a usage-volume band rather than as the basis of one.

MCP C# SDK implements both roles, the full primitive set and all three transports, putting it level with mcp-python-sdk. All three optional features are documented, but the documentation names no target specification version, describing only runtime negotiation between client and server, so the missing version citation is the only gap left.

• https://raw.githubusercontent.com/modelcontextprotocol/csharp-sdk/main/docs/concepts/capabilities/capabilities.md recorded 2026-09-17

  The capabilities documentation: server capabilities "Tools - Server exposes callable tools", "Prompts - Server exposes prompt templates", "Resources - Server exposes readable resources", plus Logging and Completions; client capabilities "Roots", "Sampling" and "Elicitation". It frames versioning as negotiation: "During connection setup, the client and server negotiate a mutually supported MCP protocol version."

• https://raw.githubusercontent.com/modelcontextprotocol/csharp-sdk/main/docs/concepts/transports/transports.md recorded 2026-09-17

  The transports documentation: "Three transport mechanisms are supported: stdio, Streamable HTTP, and SSE (Server-Sent Events, legacy)", with "Legacy SSE endpoints (/sse and /message) are disabled by default".