Previously SecretPancake on Feddit
There is actually an extension to JSON: https://json5.org/
Unfortunately only very few tools support that.
When I used a similar feature in Ice Cubes (Mastodon app) it generated very detailed but ultimately useless text because it does not understand the point of the image and focuses on things that don’t matter. Could be better here but I doubt it. I prefer writing my own alt text but it’s better than nothing.
No arrays are not allowed. Attributes can only be strings. But the children are kind of an array.