EggPlant API and Request bodies

Hey there,

What I'm trying to do is to use a JSON as a request body in a POST request in EggPlant API.
I thought I could do this by having something like:
put JSONname into api().requestBody

however the api().requestBody isn't recognised in this command however I am able to log api().requestBody as a standalone. Any suggestions on how I can build a requestBody without manually entering it?
To add, i've also tried:
set JSONname to api().requestBody
but when I log api().requestBody it is empty :(
I've managed to do this now, for anyone wondering it is
Testname(requestbody: value)
I haven't managed to find out how to just update 1 field within the request body but this overrides the whole requestbody