It's not appropriate to edit based on a guess. Make the OP clarify the question themselves.
Why? Because we're also trying to train new users on how to use the site. And worst case, you bait people into bad answers when you guess wrong.
If the OP never bothers to come back to clarify their question - then what good are answers going to do them anyway? Patience can be hard, but it is rewarding.
If someone else guesses at the tag, revert or flag it and explain why.