Hi @jekyem ! Sorry for the late response. There is currently no way to know if each currency can be deposited or withdrawn via our API. This is really an interesting request and we recommend that you post this in the Feedback Section of the Forum as most new features and improvements to Coinbase come directly from feedback like yours, so it’s very valuable to us.
As for the TBTC, new deposit address generation is currently turned off (intentional) but withdrawals are still live and trading is also not supported. You can also check/confirm it on this link. I hope this helps. Thank you!