Sorry for the mispelling of "language", actually in my app I spelled it right ^^, the screenshot was made on purpose for this post, as in my app it is a c# class.
I tried adding objectProperties the way you mentionned, but I got a 400 Bad Request with it. Btw not sure that would have helped since objectProperties is a array of string, so enclosing each properties with quotes is the right way I think so ?