How to use content of http.body

I have an automation that trigger an HTTP Request to get informations on a job :

host.com/fmeapiv4/jobs/{user.id}

The HTTP request is send and I get my response : 

{"id":122,"engineHost":"localhost","engineName":"localhost_Engine1",... ,"elapsedTime":29176,"cpuTime":7687,"cpuPercent":26.346997532218264,"peakMemoryUsage":186314752,"lineCount":2439,"warningCount":27,"errorCount":0,"remoteEngineName":"","remoteEngineJobLogUrl":""}

I would like to send an other http request based on the content of the body response :

host.com/fmeapiv4/accounts/{runtimeUserID}

The runtimeUserID key is a key in the http.body attribute which is a JSON value.

I cannot extract some portions of this JSON

I have try to get other keygs but it always failed :

• {http.body}.{runtimeUserID}
• {http.body.runtimeUserID}
• {runtimeUserID}

and lots of combinations…

Is it possible and if so, how to achieve this ?

Thank you