When developing integration to Basecamp 2 API I encountered issue that their API requires User-Agent header (to prevent getting into blacklist). I used AS:HttpRequest function in this matter. XPathNavigator header array doesn’t allow sending this type of header, it fails with this error message (in czech):
Hlavička User-Agent musí být upravena pomocí vhodné vlastnosti nebo metody.
Název parametru: name
I would propose sending this header within XPathNavigator object or setting it automatically in every http request (for example User-Agent: Origam (admin@origam.cz)