Unable to access progress token in McpTool

[aaronpowell]

Is your feature request related to a problem? Please describe.
I'm attempting to build out a .NET implementation of server-everything and one of the features is the Long Running Operation. This requires access to a progress token (https://github.com/modelcontextprotocol/servers/blob/e328131d99847e1eae33c7a6a8156fd217cf984f/src/everything/everything.ts#L406) to provide notifications back to the client.

There does not appear to be a way to access that in the McpTool method.

Describe the solution you'd like
I think there should be a way to have an argument to the McpTool method that is bound to the request context (or the equivalent _meta property from TypeScript), in the same way you can have a HttpRequest on minimal API.

Describe alternatives you've considered
I've looked at the CallToolRequestParams when creating your own CallToolHandler callback but I don't think you can get to it through that either.

Additional context
Sample Code - https://github.com/aaronpowell/modelcontextprotocol-csharp-sdk/blob/dotnet-everything/samples/EverythingServer/Tools/LongRunningTool.cs

[stephentoub]

I'm in the progress of addressing this.

[stephentoub]

(or the equivalent _meta property from TypeScript

The CallToolRequestParams is available to an McpServerTool now as of #89, so if _meta is exposed on that, this issue will be addressed.

[aaronpowell]

Just playing around with the changes in #89 and it's not exposing the _meta property from the incoming request.

Here's a screenshot of the request running:

In the jsonString variable we can see the _meta is available, along with the progressToken, but the CallToolRequestParams doesn't deserialize that property.

If we added it there we can expose it.

[aaronpowell]

If I'm reading the JSON schema correctly, part of this is coming from here: https://github.com/modelcontextprotocol/specification/blob/main/schema/2024-11-05/schema.json#L771-L806

The JSONRPCRequest type defines the _meta property on params as expected, and the description of it matches the description in the TypeScript SDK and Python SDK implementations (probably the others, I didn't dig that far).

Going through the Python SDK, it seems that they use a base class for many of the request types (which has that property on it), so would it make sense to create a base class in C# that has the _meta property deserialized to it?

[aaronpowell]

Created a local branch where I deserialize the _meta property and this code now works:

[McpServerToolType]
public static class LongRunningTool
{
    [McpServerTool, Description("Demonstrates a long running operation with progress updates")]
    public static async Task<string> LongRunningOperation(
        IMcpServer server,
        RequestContext<CallToolRequestParams> requestParams,
        int duration = 10,
        int steps = 5)
    {
        var stepDuration = duration / steps;
        var progressToken = requestParams?.Params?.Meta?.ProgressToken;

        for (int i = 1; i < steps + 1; i++)
        {
            await Task.Delay(stepDuration * 1000);

            if (progressToken is not null && server is not null)
            {
                // Send progress update
                await server.SendMessageAsync(new JsonRpcNotification
                {
                    Method = "notifications/progress",
                    Params = new
                    {
                        progressToken,
                        total = steps,
                        progress = i
                    }
                });
            }
        }

        // Return the result
        return $"Operation completed in {duration} seconds with {steps} steps.";
    }
}

Would you like me to PR that on top of #89 (the deserialization, not the whole "everything server")?

[stephentoub]

not the whole "everything server"

Would it make sense to add the everything server, in samples or tests or something?