Custom GPT calling API, should I retrieve all data or a subset?

So how the heck does the GPT decide how or when to use an Action? I’ve been grappling with getting an action to run with every message recently and I feel like there has to be a reliable solution to directing a GPT toward a given action for certain circumstances.

How? I’ve gotten it to mostly run at every message, but I can’t get it to actually call the action reliably. It just shows me an “Unknown plugin” most of the time. Frustrating