[Feature]: Add support for an MCP server package type

[joelverhagen]

Related Problem

It is technically possible today to package an MCP server as a NuGet package.

• Create a CLI tool project
• Use the https://github.com/modelcontextprotocol/csharp-sdk to implement it
• Pack it as a CLI tool nupkg
• Upload to NuGet.org
• Use it in VS Code using https://github.com/Redth/npx-dntx (until Support ephemeral execution for dotnet tool run similar to npx, docker, and uv dotnet/sdk#47517 or Add a one-shot execution mode for .NET tools a la npx dotnet/sdk#31103) are implemented.

However this has a couple of problems:

1. These are just CLI tools on NuGet.org so they aren't discoverable as MCP servers.
   • This can be solved by defining a package type for MCP server packages.
2. Single-shot execution is not supported first class in .NET SDK.
   • I think this will be solved for .NET 10 per Add a one-shot execution mode for .NET tools a la npx dotnet/sdk#31103 (milestone is set to .NET 10 SDK backlog)

We can implement the UI changes on NuGet.org behind a feature flag/flight for internal testing until single shot execution is supported. Or we can use the npx-dntx for now.

If VS Code supports microsoft/vscode#249370, then we could perhaps avoid the single-shot command requirement, but I'm not sure.

The Elevator Pitch

First, define a package type for MCP server (work with .NET MCP folks for this), McpServer. In .NET 10, this can be added to the existing DotnetTool package type using <PackageType>MyCustomPackageType</Package>, via dotnet/sdk#48039. This is also possible with <= .NET 9 with an MSBuild workaround mentioned here: NuGet/Home#14220.

Second, make package details page aware of it.

To enrich the command palette (copy-pastable JSON), we will read a server.json from the root of the .nupkg which describes the parameters used to start the tool. The schema of server.json is defined by the MCP registry (shape, sample).

Third, make the search experience recognize the type, so this does not appear:
https://www.nuget.org/packages?packagetype=McpServer

Finally, or (once there is a sufficient "seed" of MCP servers on NuGet.org), make it an option in the package type filter:

Additional Context and Details

• E2E experience spec
• Single-shot tool execution - available on .NET 10 preview 6 (July 8 ETA)
  • Design
  • Implementation
• NuGet.org experience (this issue)
  • Ingest server.json when PackageType = McpServer
  • Enrich package details page with VS Code mcp.json, mapped from server.json
  • Add McpServer as a recognized package type for package server
• Tutorial doc + blog
  • Tutorial PR: Add quickstart for minimal MCP Server using .NET and publish to NuGet dotnet/docs#47007
• .NET project template
  • Issue: Create an MCP server template following package conventions dotnet/extensions#6518
  • PR: Create a project template for an MCP server dotnet/extensions#6547
• Add support for NuGet in MCP Registry
  • Add support for .NET / NuGet based MCP servers modelcontextprotocol/registry#126
• Add support for NuGet MCP in VS Code
  • https://github.com/microsoft/vscode-copilot/issues/15329

[ErikEJ]

@joelverhagen I publish a MCP server today, basically a command line tool with MCP server enabled - do not understand the npx requirement (in fact do not understand what it is)

https://github.com/ErikEJ/SqlServer.Rules/blob/master/tools/SqlAnalyzerCli/readme.md#github-copilot-mcp-server-preview

[joelverhagen]

@ErikEJ, how are you invoking your MCP server? What IDE/agent UI are you using it in? The npx part is a workaround to get a .NET CLI tool + MCP server running in VS Code which only supports a single command (.NET tools require two commands to run today).

[ErikEJ]

@joelverhagen In Visual Studio or VS Code - have a look at the link to my docs.

Or my blog post: https://erikej.github.io/mcp/dotnet/copilot/2025/05/06/mcp-dotnet-copilot.html

[joelverhagen]

I see, you have the install step first, outside of the IDE. Ideally we could install + run in a single shot, like npm/Python/docker have.

[ErikEJ]

@joelverhagen Thanks, reading up on the links now. Is it really a show stopper?

[joelverhagen]

I don't think it's a showstopper. But it's a worse experience then JS/Python/Docker. We would have to instruct the end user to run a certain global install command, so the mockup above for copy-pastable JSON.... it would need to be a two part thing: run the global install, then copy paste the JSON. I think.

[joelverhagen]

I have drafted a public proposal related to this. @ErikEJ - I'd love to hear your thoughts, if you have time.
NuGet/Home#14344

[ErikEJ]

@joelverhagen Looks great, looking forward to help with this!