Use gron for adhoc, then jq to script once you know what you need to do.
I also find VisiData is useful for adhoc exploring of JSON data. You can also use it to explore multiple other formats. I find it really helpful, plus it gives that little burst of adrenaline from its responsive TUI, similar to fx and jless mentioned.
For my toolbox I include jq, gron, miller, VisiData, in addition to classics like sed, awk, and perl.
- https://github.com/saulpw/visidata - http://visidata.org/
Also there is a great introduction: - https://jsvine.github.io/intro-to-visidata/ "Intro to VisiData Tutorial" by Jeremy Singer-Vine