500 Error when setting up Swagger in asp .net CORE / MVC 6 app

I'm trying to setup a basic swagger API doc in a new asp .net CORE / MVC 6 project and receiving a 500 error from the swagger UI: 500 : http://localhost:4405/swagger/v1/swagger.json

My startup class has the following code in it:

using Swashbuckle.SwaggerGen;
using Swashbuckle.SwaggerGen.XmlComments;
using Swashbuckle.Application;
....
public void ConfigureServices(IServiceCollection services)
{
  ...
  services.AddSwaggerGen();
  services.ConfigureSwaggerDocument(options =>
  {
    options.SingleApiVersion(new Info
    {
        Version = "v1",
        Title = "Blog Test Api",
        Description = "A test API for this blogpost"
    });
  });
}

and then under Configure:

public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
{
....
  app.UseSwaggerGen();
  app.UseSwaggerUi();
....
}

When i build and run the project, the UI will come up when i go to swagger/UI/index.html, but the 500 error above is displayed. When i go to the swagger/v1/swagger.json link, console gives the following 500 error: Failed to load resource: the server responded with a status of 500 (Internal Server Error)

Is there any way i can figure out the root cause of the 500 or enable any additional debug in swagger to figure out why it's throwing this error? Based on some of the tutorials i've looked at, only what i have in startup is required for a base implementation. Please let me know if i can provide any additional information.

EDIT: this is for rc1, and may not be relevant to the new netcore 1.0 currently out (6/29/2016)

Solution

Initially I got a 500 error too. Deep down in the stacktrace it said: System.NotSupportedException: Unbounded HTTP verbs for path 'api/hotels'. Are you missing an HttpMethodAttribute?

It turned out I was missing a HttpGet attribute for one of my api methods:

[Microsoft.AspNetCore.Mvc.HttpGet]

also if you used a method with a parameter like this "Get(int id)" you will get the same error without an explanation so you need to add it into the decoration "[HttpGet("{id:int}")]"