No, I’m considering player actions.
<snip>
Yes, the players acted and it is significant, and the GM is considering that. But so many other factors being considered don’t come from the players… they come from the GM.
So when we see how the GM decides, given that he’s determined nearly all the things that matter, I think it’s silly to diminish the role the GM is playing in all this.
Here's my take, by way of an illustrative story of course!
Suppose that I walk up to you and insult you. I prompt you to action. Maybe you laugh and walk away. Maybe you abuse me. Maybe you punch me. Maybe you take pity on me.
It seems fair to say that I have no complaint that you respond - I've provoked you, after all. Perhaps some responses - punching - are out of bounds for broader social/legal/etc reasons. But I can't reasonably expect you to remain inert in response to my provocation.
Nevertheless, you are the author of your response. There's no particular thing that
I made you do.
Turning from the story to RPGing:
When the players declare actions, the GM has to respond. That's not in doubt, I think.
If the GM hasn't got a planned response, then they have to come up with something. Their are all sorts of ways they can do that.
But the fact that it wasn't planned, and likewise
the fact that the GM didn't even anticipate the prompt, doesn't change the fact that it is the GM who is authoring whatever it is that they come up with.
What is interesting is to look at the principles, heuristic, rules, expectations, formal and informal norms, etc that guide and govern the GM as they make a decision. Depending on what those are, the one who prompts the GM's response may exercise more or less control over things.
To go back to my story: if I know that you are a violent person with a hair trigger person, and I want to get you in trouble, then maybe I insult you
so that you will throw a punch, so that I can then have you arrested for assault. You're still the author of your action; but I've played you, manipulated you, goaded you.
In ordinary interpersonal relations that sort of manipulation is often unpleasant (not always, though - when I extend my hand to you, thereby and knowingly prompting you to shake my hand, that may just be common courtesy). But in game play it's
how we make things go - for instance, in a RPG the GM describes something to the players
in order to prompt them to declare actions for their PCs.
I see the relationship between player agency and the GM's control over play in the terms I've set out. If the players know how the GM will exercise their authority, and can use that knowledge to prompt certain responses, they are exercising agency. If they don't, then they are exercising considerably less agency - they are prompting the GM to respond, sure, but in a rather blind way. They don't know what they're going to get in response.