Besides's this projects cli, jp (https://github.com/jmespath/jp), I see jl (https://github.com/chrisdone/jl) and jq (https://github.com/stedolan/jq/) in the comments. I wonder if anyone has had experience with all three (or even just one) and can comment on their experiences?
jq is by far the best developed and has the most intuitive syntax, but it doesn't have a formal spec for its language.
I have been maintaining https://github.com/kislyuk/yq, which wraps jq with a transcoder for YAML and XML.