I did what you suggested and ended up with

{
   "args": {},
    "data": "",
    "files": {},
    "form": {},
    "headers": {
    "Accept-Encoding": "gzip", "Host": "httpbin.org",
                      "Referer": "http://httpbin.org:80/Polka.Api/REST/SendFax",
                     "User-Agent": "Mozilla/4.0(compatible; Cache;)"
                       },
    "json": null,
     "origin": "216.119.54.2",
      "url": "http://httpbin.org/post"
    }