Do you mean a keyword tool to find the best keywords online? There are many - try Google Keyword Planner for free or Semrush for a fee.
If you mean looking for keywords on Etsy, the search bar is the best tool you can use. Type in a word related to your product and see what autocompletes. Type in a letter after that word for more keyword phrases. Imo, this would be the most accurate since it's based on how buyers actually search here. There are a lot of keywords that don't autocomplete even though you think they would.
If you mean keywords in ads, you're SOL because Etsy adds in a ton and even if you remove the irrelevant ones, it's been reported Etsy adds them back.
