On Special:EnableStructuredDiscussions
it says

Page to enable Structured Discussions on

OK, understandible. Alas, the next line:

Initial description of Structured Discussions board (wikitext)

Users have no idea what to write here. Nor if it is optional or not.
Users often simply intend to convert an existing page into a Structured Discussions page,
hence expect whatever this is asking, to be done for them.

The help button doesn't explain it either.