When placed on your world, hostile ships cannot see what structures you have. This does not cloud the attack/defense/cloak numbers, but hides your buildings.

i dont see much of a point to it unless it would also hide the population number in which case +1

yeah, unless it hides special structures like pylons or council bases, this arti would be useless. who cares how much production you have on it if you still get accurate defense stats after using it.

The whole point is that it hides the actual structure list. Can't see any special artifacts like council bases, invasion defense, etc, to know what you're really walking into.