Web component - post text with arguments skipped by App Inventor

[Blacktea]

(new post cause i don't know how to set the last one "not resolved")

Hi, i'm building up an App that send and receive data from Booked (http://www.bookedscheduler.com) .

API are supported (as described in http://allsaintsbrookline.org/schedule/Web/Services/ )

I'm going to create a new user via-API but it seems that App Inventor doesnt mind of what i put in Posttext.text block.

The API gives me back all the registered users (that is what API have to do if i dont post arguments)

It is strange cause the authorization process uses the same blocks (as seen in the attached image) and works well.