I just noticed the new
Research Assistant badge on SO. The description says that to get it you have to
Edited 50 tag wikis. Does adding descriptions to existing tag wikis that have no description count towards this? Also does creating tag wiki's count toward this?
Yes. An edit includes creating the wiki description.
You need to edit the wiki body for it to count towards the badge. Excerpt edits don't count.
For more information see this answer.