How to delete all but certain values from many JSON files?

i’ve used another Terminal utility to download all my videos from Youtube (youtube-dl if interested). with these, are created a JSON file for each video file. inside these JSON files is a LOT of junk. but there are 3 items/values/categories(?) that i want to keep, the rest can be deleted.

those things are
{“upload_date”: “value”,
“fulltitle”: “value”,
“description”: “value”}

so i either need to:

  1. delete all but these 3 items & save the file, or
  2. extract these 3 items to a new file & delete the old one.

hoping for (but haven’t been able to find) a Mac app that can batch do this for all the files at once.
have a Terminal script (that’s EASY, as i don’t know about all that),
an Automator script (again, that’s EASY) that’ll do it all.