It wasn't a commercial tool. It was a phantom script, whispered about in encrypted forums, capable of "stitching the shattered."
Look for a file named master.m3u8 , playlist.m3u8 , manifest.mpd , or stream.mpd . Click on it. In the "Headers" sub-tab, copy the Request URL .
Because being able to download something doesn't always mean you should. But when you should, it's good to know how.