I'm using Fire App Builder and have a variety of macros to fill in generating a url for my ad server (LKQD) in order to deliver a VAST tag to the user. I understand how to put in a static URL, but I'm not sure (a) how I can dynamically change that URL each time the app requests an advertisement from the ad server, and (b) where I can get the information I need to fill the URL macros—things stored in my XML/MRSS file like video duration or video title, which I'm not sure how to retrieve and access and put into the URL, as well as device–specific things like display width and height and device type/name.
I'm a real beginner at this (have exclusively done RSG/BrightScript development in the past) and so the answer to this may be obvious, but the documentation provided by Amazon is extremely limited. Thanks for your help.