The Firebird
Hero
Imo--the platonic ideal would be to have everything fleshed out ahead of time. Obviously this is not practical, so instead the DM will focus on high likelihood areas.I said house. Do you flesh out each and every single house in your world, just in case the players decide they want to break into one? Do you flesh out every single person who lives in the world, just in case the player says "Hey, you there!" to one and starts asking personal questions.
The point isn't that it's bad for the NPCs to respond. But that the NPCs should be specified ahead of time so that the players have meaningful choices, rather than after the roll where the most important thing is the dice.So if the PCs are trying to stealth somewhere so the NPCs don't hear them, and they fail, indicating they make noise, you won't have the NPCs react to the noise?