Ready

The Ready activity lets the acting person choose the trigger for their readied action. However, you might need to put limits on what they can choose. Notably, the trigger must be something that happens in the game universe and is observable by the character, rather than a rules concept that doesn't exist in-world. For instance, if a player says, “I Ready to shoot my sonic rifle at her if she uses a concentrate action” or “I Ready to attack him if he has fewer than forty-seven Hit Points ,” find out what their character is trying to specifically observe. If they don't have a clear answer for that, they need to adjust their action.