How freeradius responds in json format to the request to authorize

[Fiorella De Luca]

Hello! I am a new Freeradius user. I'm participating in the Google Summer Code and I'm working on an OpenWISP project regarding the creation of a freeradius web interface. This app Django-freeradius will be a web interface to a manage freeradius database using a Django Rest framework . I 
I installed FreeRADIUS Version 3.0.12 on Ubuntu. 
I am using rlm_rest So I can configure freeradius to delegate some or all of its operations (authorization, authentication, accounting, mail order) to a REST API. 
But I can not understand how freeradius responds in json format to the request to authorize . 
I tried to accept the user with Auth-Type: = Accept
And for the user to refuse: Auth-Type: = Reject but it does not work. If anyone could give me an explanation
I'll be more than happy. Thank you!