Using Umbraco Forms and I'm looking to add a Workflow that will post form to URL. I have the following setup

Name: Post form to URL Type: Post form to URL Url: http://domain.com/umbraco/api/subscribers/get Method: GET Fields: (initially blank - is there any documentation for this?)

Below is the code for my post URL which is initially setup just to see if the URL gets hit

public class SubscribersController : UmbracoApiController {

        public HttpResponseMessage Get() {
            LogHelper.Debug(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType, "GET");

            return new HttpResponseMessage(HttpStatusCode.OK)
            {
                Content =
                new StringContent(JsonConvert.SerializeObject(new
                {
                    msg = "GET"
                }, Formatting.None))
                {
                    Headers = { ContentType = new MediaTypeHeaderValue("application/json") }
                }
            };
        }
}

The form submits successfully as entries are being stored, but the post form to URL is failing on submit as indicated the UmbracoTraceLog below

2015-07-27 17:06:56,737 [39] ERROR Umbraco.Forms.Data.LogHelper - [Thread 30] Forms: workflow 'Post form to url' failed on Submitted
System.Net.WebException: An exception occurred during a WebClient request. ---> System.Net.ProtocolViolationException: Cannot send a content-body with this verb-type.
   at System.Net.HttpWebRequest.CheckProtocol(Boolean onRequestStream)
   at System.Net.HttpWebRequest.GetRequestStream(TransportContext& context)
   at System.Net.HttpWebRequest.GetRequestStream()
   at System.Net.WebClient.UploadBits(WebRequest request, Stream readStream, Byte[] buffer, Int32 chunkSize, Byte[] header, Byte[] footer, CompletionDelegate uploadCompletionDelegate, CompletionDelegate downloadCompletionDelegate, AsyncOperation asyncOp)
   at System.Net.WebClient.UploadValues(Uri address, String method, NameValueCollection data)
   --- End of inner exception stack trace ---
   at System.Net.WebClient.UploadValues(Uri address, String method, NameValueCollection data)
   at System.Net.WebClient.UploadValues(String address, String method, NameValueCollection data)
   at Umbraco.Forms.Core.Providers.WorkflowTypes.PostToUrl.Execute(Record record, RecordEventArgs e)
   at Umbraco.Forms.Core.Services.WorkflowService.ExecuteWorkflows(List`1 workflows, RecordEventArgs e)

Any ideas on what might be wrong?