The gotcha for this is that you have to actually use the resources on your free instance or they will reclaim it. I use my instance as a Minecraft server so it utilizes about half of the 24GB RAM you get. For a very light compute task like a chat bot, it might be difficult to keep the instance from being reclaimed.
Idle Always Free compute instances may be reclaimed by Oracle. Oracle will deem virtual machine and bare metal compute instances as idle if, during a 7-day period, the following are true:
CPU utilization for the 95th percentile is less than 15% Network utilization is less than 15% Memory utilization is less than 15% (applies to A1 shapes only)