I've built a few toy apps that use json as intermediate formats and I've found JsonPath to be pretty effective at building ad-hoc queries. I wrapped it in a thin layer of python for command line use if anyone is interested.

Syntax and the real meat: http://goessner.net/articles/JsonPath/

My rough-and-ready wrapper: http://github.com/skorgu/pyjsonpath/tree/master

Its error handling is a little odd, and it doesn't detect unexpected commands.

    $ resty 42; echo $?
    resty: curl returned error 42
    0
    $ 

(curl was never called.)

If you look at the bash source code, resty uses curl.

I looked at the source code; that's how I spotted its bugs, including the one above. :-)