The divination spell states:
Similar to augury but more powerful, a divination spell can provide you with a useful piece of advice in reply to a question concerning a specific goal, event, or activity that is to occur within 1 week.
I'm not sure what limitations the language about "a specific goal, event, or activity" imposes. The immediate motivation for this comes from a Kingmaker campaign that I'm currently running. After an attack on their capital, my players came up with the idea of casting divination once a week to ask "Will anything attack our kingdom this week?"
I'm trying to figure out if this is specific enough, and if not, what would be specific enough. On one hand, it's not a specific event - they aren't expecting any particular attack. On the other hand, it's arguably a specific goal - keeping their citizens safe from large-scale threats.
Also, I expect my players to use divination many times during this campaign, so I'd like to know how this language limits the spell beyond this one case.
One limitation I've imposed so far is that sufficiently obscure or protected knowledge might be beyond divination's power. For example, "Where is the legendary artifact called 'The Eye of Ragnarok' hidden?" would yield the equivalent of "I don't know". I've seen this limitation mentioned before in published adventures, and my players seem fine with it.