I finished writing my take on Discern Realities for Stonetop recently, and tried to address a lot of these questions. Nothing that hasn’t been said yet, I don’t think, but maybe it’s useful anyhow?
Answer honestly, generously, and helpfully. Rely on your prep and sense of the fictional space to guide you. Sometimes (often), you’ll need to make up details on the fly. These details become true parts of the fiction! If you aren’t sure how to answer the question, ask the player for guidance. “Well, the old coins are obviously valuable, but what sort of thing were you looking for?”
Remember to begin and end with the fiction. Don’t just tell them that Siowan is about to betray them; describe how Siowan is acting nervous and keeps glancing at the door, like he’s expecting someone to burst in any second. Alternately: answer their question directly and simply, and ask them what details lead them to that conclusion.
Adjust your answers to reflect the fiction. The move isn’t magic; it doesn’t let the characters know things that they couldn’t. A quick scan of the room from the entrance should give less-specific and less-useful insights than if they get in there and interact.
You’ll feel pressure to give answers that are surprising or revelatory, but often the best answer is the obvious one. “ What here is valuable or useful to me?” “Those gold coins that I described earlier. Everything else is basically junk.” And sometimes the honest, helpful answer is basically “nothing.” “What should I be on the lookout for?” “Not much. This place seems quite safe.” “Who or what is in control here?” “No one. It’s a damn free-for-all.” Such answers remove doubt and clarify the situation (and remember, they get advantage on their first roll to act on the answer).
And as an example:
The PCs are staring up at a crinwin nest. They ask about its size (“as big as a house back in Stonetop”) and the tree it’s in (“like a redwood sequoia, the lowest bough maybe 60 feet up”) and whether they see anything moving about the nest (“nope”). Then Rhianna asks “Can I tell if there’s been activity recently? We’ll look for tracks and whatnot.” That’s looking for insight, not just data, so she’s Discerning Realities.
She rolls +WIS (with advantage as her crew Aids her) and gets a 10+. “Is the nest still active? Like, are there any signs of recent activity?” she asks.
That’s two questions, neither of which are on the list. “Are you asking ‘what happened here recently?’ Or ‘what should I be on the lookout for?’”
“Oh, yeah. Um, what should I be on the lookout for? Specifically, should we be on the lookout for crinwin right now?” I say no, nothing to be on the lookout for. The nest seems to be unoccupied and even damaged. Geralt (from her crew) calls her over and shows her the crinwin bodies he found, rotting away in the brush.
“Whoa. Okay… what happened here recently?”
I tell her that they find more crinwin corpses, and a few that appear to have killed each other. “A few weeks old, at least. But there aren’t enough corpses for a full a nest. And you find signs of crinwin dragging off other crinwin, in the same general direction they carried off Pryder.”
“What the hell?” spits Rhianna. “Who or what is really in control here? Like… who or what is behind this?”
I know that Sethra the swyn (a giant, hypnotic, monkey-headed snake) is behind the attack., but I don’t see how Rhianna could possibly deduce that. So, I give her as useful of an answer as I think the evidence would allow: “Down the path a little, you spot, like, a… scale? Like a drake scale, but bigger. Flatter. More like a snake, maybe? And it’s got a golden shimmer to it.”
“Do I recognize it?” Rhianna asks, and I say “I don’t know, sounds like you’re Spouting Lore?” And she agrees, and rolls with advantage for following up on an answer.