1. Does anyone search for it?
Type the category into Google. Are there shopping results and competing ads? Competition is a good sign — it means the demand pays.
2. Can the margin carry a click?
Work out gross profit per order. Compare it to plausible CPCs in your category multiplied by a realistic number of clicks per sale. If the arithmetic is impossible, no agency changes it.
3. Would a reviewer trust the store?
Contact details, policies, honest shipping. If not, you will be suspended before you learn anything.
Three yeses and Google is worth testing. One no and you have saved yourself a month.