It doesn't break any rules, so yes, it's allowed.
However, you can ask a better question by including more details. The competitive scene is very broad and spans multiple generations and unique battle formats. You should narrow down the question with this in mind. For example, "How viable is Krookodile in Sw/Sh UU?" is much better than "How good is Krookodile in competitive?"
Also mind that people will probably be annoyed by questions like "Is Ledian viable in Gen 8 AG?" that show really terrible awareness of what the battle format is.
