Thanks so much for the kind words! 😊
TumblBee is designed to always grab the original version of any media that’s passed to it. In newer posts, these original-size media are marked with has_original_dimensions: true, but this field is absent on posts made before the rollout of NPF and the new API (2018). To get around this, I’ve chosen to instead grab the first media file provided for any given block. Since media sizes are returned in descending order, in my testing, this always returns the original media file. If you should see anything different in your testing, though, please do report it as a bug so I can look into it.
JSON format is a great suggestion—thank you! I’ll see about getting that added sometime in the next few days!