Some doubts in the actual use of fwknop

[IT-Highmore]

hello, guys, I am a new fwknop learner!
I have implemented a simple SPA on Ubuntu based fwknop，here are some immature questions want to ask !

1. I noticed that each SPA packet can contain a series of optional fields, so how to customize the content in the SPA packet, for example, the client carries the token and sends it to the server?

2. When the server receives the client's SPA packet, can it return some information to the client?for example, tell the client what permissions it has.

3. If the second article is true, how to pass or store the returned information?