How to add description in table from script

Hello,
I wonder if there is any way to fill the "description" field available in the "design" view, but from a script. In fact, I want to make a script to create tables and add description to these tables and columns. The goal of this is that so, I could generate the documentation with schema spy in a html page. I already tried addExtendedProperty to add some comment, but schema spy ignore them.

So, to make it clear, I just want, within a script, to fill the "description" field available in the "design" view. Is this possible ? How could I do ?

Thank you,
David