I've been receiving a number of questions with regard to exploiting the trading system to gain a gpt advantage over an AI civ. Intentionally pushing the AI into a negative gpt situation is an exploit. Per the GOTM webpage:
It is best to avoid the appearance of exploitation when making trades, but if you have a question about a trade and whether it is exploitive, PM me first.There are some types of exploits and bugs listed here that are specifically allowed or disallowed. If you wish to take advantage of a bug or exploit not listed then you must contact the staff via Private mail for a ruling on whether or not it will be allowed.