If it's a domestic flight, all the "Flexible" fares are refundable with no fee. There's no need to upfare to "Fully Flexible" fares which have no advance purchase requirement if you just want the ability to cancel and get a full refund prior to flight on domestic flights. Flexible fares with a fee to refund are only found on certain international routes. While fees for refund will be called out in Fare Rules in Penalties section, you can often also identify them simply from the fare basis codes. In the case of TATL fares, AA refundable fares with no fee for refund will end in a 9, while AA refundable fares with a fee will end in a 3.

A lot of people seem to want to make things more complicated than they actually are. The magic words for refundable fares in the fare rules is "Cancellations Permitted" in the Penalties section. This language for refundable fares is common across all airlines (not just AA). If it says Cancellation Permitted and there are no fees listed for refund in Penalties section, it is fully refundable with no fees. In some cases, you need to cancel before departure or the fare becomes non-refundable. This will also be called out in fare rules. In the case shown below for the MLX7T0M9 fare, you can still get a refund if you wait until after departure to cancel as indicated by the allowance for refunds in "NO-SHOW" cases.