JSON key reducer and formtter in Ruby

I am facing a situation where it seems helpful to have a gem that can format the JSON that comes as a response from any API. For example I may make a call to fetch some data but I don't need all the fields, instead I need to create a new JSON by parsing the original one to only include some fields and also be able to select only some of nested fields from arrays or array of arrays inside that JSON. The result of the reduced JSON can be a JSON that has only one level of nesting. Can you please help me if there is an existing gem in Ruby to do this?