The descriptions are shockingly detailed. I wish there was a way you could add these descriptions to the metadata of all the photos in your library, it would be an amazing way to add rich searchable data. In particular, asking Siri to "show me photos of " where x is a thing that the photo descriptions does recognize, doesn't always work.
Just so you know, you can search the photos libraries with all sorts of ML-generated metadata (eg mountains).
Yes but the things that the image descriptions recognizes is a far longer and more detailed list than the searchable objects.