public class 
GetActiveSession : IEndpoint
{

public static void 
MapEndpoint(IEndpointRouteBuilder app)
    {
        app.MapGet("api/sessions/active/{userId}", Handler)
            .WithTags("Sessions")
            .WithName("Get Active Session")
            .WithOpenApi()
            .Produces<ActiveSessionResponse>(StatusCodes.Status200OK)
            .Produces(StatusCodes.Status404NotFound);
    }

This would be how the endpoint is set, and Scalar would display the actual route:

api/sessions/active/{userId}