Here is the sample of code that I am using to call the API.
System.Net.HttpWebRequest request;System.IO.Stream stream;System.Exception sysEx;request = System.Net.WebRequest::Create('URL') as System.Net.HttpWebRequest;request.Method = 'POST';request.ContentType = 'application/json';System.Net.WebHeaderCollection headerCollection = request.Headers;headerCollection.Set('Name', 'Value');var utf8 = System.Text.Encoding::get_UTF8();var byteArrayPayload = utf8.GetBytes('{key1:value1,key2:value2}');try {using (System.IO.Stream dataStream = request.GetRequestStream()){dataStream.Write(byteArrayPayload, 0, byteArrayPayload.Length);}using (System.Net.HttpWebResponse response = request.GetResponse() as System.Net.HttpWebResponse){stream = response.GetResponseStream();System.IO.StreamReader reader = new System.IO.StreamReader(stream);str responseBody = reader.ReadToEnd();}}catch(sysEx){throw;}