I'm not sure it's that complicated. FWIW, in the FreeSWITCH 1.2 book there is a good explanation starting on page 220. The wiki page you reference looks like it's still a work in progress so I would check the
old wiki mod_xml_curl page for possible other information. However, as long as the request has enough information for your server to act upon and respond with the appropriate XML then you're good. If you still feel like there's something lacking for documentation then perhaps you could pose a very specific question here whose answer you didn't find on the wiki.