When I was a kid my grandmother tasked me with making tea. It would have hlped if I knew how to tell decorative teapots from functional teapots.
Sometimes pots meant for purely decorative purposes will say so on the bottom of the pot. A well fitting lid and functional spout are a must and not all of the decorative ones have these.
Also some of them have holes. But others are just fancy and they don't give you any indication.
This can be the case with some really old pots. It is just hard to tell what they were supposed to be. Another factor for me is lead. I am not sure if the old pots were lead free so I test them. If you are worried about lead in old ceramic glazes, you can buy a lead testing kit. Do not use pots that are made from pewter, as it does contain lead.