When you’re designing a game, it can be helpful to ask—and answer—”what do I want my players to describe?” It’s probably not the first question you want to answer, but when you need to ask it, you know you will. It’s not quite the same as “what happens in my game” because, importantly, it’s about what details your players will dwell on, what will give the game its texture.
Once you have some answers to that question, the next thing to consider is how to get your players to actually spend some effort describing those things. This is part of what Vincent’s whole thing about “rightward pointing arrows” was about. They’re one possible technique for making the things described in the fiction meaningful and important enough that people don’t gloss over details, and thus describe what you want them to. Look at D&D: it says “describing tactical positioning is important”, and so it gives you a bonus for having the high ground. It does not say “describing how your character feels about what they’re doing is important”, and so there’s no bonus for emotional state. One gets described, the other doesn’t.
Or look at Dogs in the Vineyard. It says “you decide what details are important to describe, but it’s always important whether you’re talking, fighting, or shooting.” The system does things when you switch between those modes, but it also does things when you bring in your own traits, which you made up when you made your character.
But there are other things you can do, such as including very explicit leftward-pointing arrows. Consider Hot Guys Making Out: you can either play a card, or discard a card and draw a card. When you play a card, you describe an action your character takes (with constraints based on the specifics of the card you played), and very importantly when you discard a card and draw a new one, you describe some environmental detail. The fact that Ben recognized, in his game design, that descriptions of environmental detail were important to giving the game the sense of space and slowness that it calls for, and indicated to players when and how to include such narration, is really great.
So, let’s talk a moment about Piece of Work and Et in Arcadia Ego.
In the first, what’s important to describe is what tools you use, and why you do what you do. Every time you roll, the game asks you about those things: you have to select one die based on the gear you use, another based on your motivation, and another based on how big a deal what you’re doing is (is it just for you, or does it go “all the way to the top”?). That is, in essence, a rightward pointing arrow. You could always take the biggest dice, but it would depend on certain things in the fiction being true, and so, by taking those dice, you have to think about what that means in the fiction.
Arcadia has a system a bit more like the leftward arrows of Hot Guys Making Out. When you play a card, it either follows suit, which means you agree with the person who started the whole thing; breaks suit, which means you suppress your disagreement and describe some reaction or action that makes this clear (“My jaw tightens at the mention of Mr. Hughs, but I say nothing.”); or play a trump, which means that you manage to voice your opposition, in socially opprobrious language. What you describe is dependent on what card you put down.
So, what do you want people to describe in your game?