Follow my previous post about Web API here is a little bit more on Help Pages and an interesting thing that isn’t mentioned anywhere.
For a complete guide on how to enable help pages you can read the post on: http://www.asp.net/web-api/overview/getting-started-with-aspnet-web-api/creating-api-help-pages
One thing that I have noticed with Web API is that when you are using HttpResponseMessage as your return type there is no documntation generated for it.
In order to get the documentation you will have to add an attribute that tells web API what type of model it can expect as part of your return type.
Just add the attribute: [ResponseType(typeof(Your_Class))] and your documentation will now reflect the return type sent along with your Http Response.