Hello? Anyone out there?

The Contact Other Plane spell in DnD is a bit of a problem.  It reads as follows:

You mentally contact a demigod, the spirit of a long-dead sage, or some other mysterious entity from another plane. Contacting this extraplanar Intelligence can strain or even break your mind. When you cast this spell, make a DC 15 Intelligence saving throw. On a failure, you take 6d6 psychic damage and are insane until you finish a Long Rest. While insane, you can't take Actions, can't understand what other creatures say, can't read, and speak only in gibberish. A Greater Restoration spell cast on you ends this effect.

On a successful save, you can ask the entity up to five questions. You must ask your questions before the spell ends. The DM answers each question with one word, such as yes, no, maybe, never, irrelevant, unclear (if the entity doesn't know the answer to the question). If a one-word answer would be misleading, the DM might instead offer a short phrase as an answer.

My character, a wizard, has just gotten this spell and I am going to be using it as often as possible.  Many people would be intimidated by a difficult saving throw where if you fail it you go insane, but that bothers me not at all.  I have a monstrous +11 Intelligence saving throw and two bards in my party to grant me Bardic Inspiration to help my saving throw along.  I can only fail on a 1 or 2 on a d20, and even then I fail only if I roll quite low on the Bardic Inspiration die.  I think the game designed this spell to be potent and the thought was that the saving throw vs. insanity would rein it in but that doesn't work against me.  It is even a ritual spell, so in theory I could just sit around casting it over and over again all day if I wanted to.

This presents real problems.  I can spam questions to figure out where my enemies are, what is in the next room, where treasure is located, all kinds of crazy things.  If, for example, I wanted to locate a particular person I could just play twenty questions, starting with "Is Blorfmap the bloody north of me right now?" and after a few castings I could determine which rock Blorfmap is sitting on. 

That seems like a real problem for campaign design.  It gets even worse if I start asking questions like "Is Everick planning on breaking his promise to me?" and effectively getting mind reading in the bargain.

Of course the GM could just start replying "Unknown" to all kinds of questions and refuse to let me figure anything out this way but that feels frustrating.  I don't mind constraints, but I don't want a system where every time I think of a clever solution to a problem the GM just flat out says no.  Giving the enemies informational plot armour is weak.  I don't like a system where I can figure out lots of stuff but as soon as it becomes plot relevant it gets locked out. 

Many other solutions keep the power of the spell in check but also make it unusable.  For example, having the entities you contact lie you to if they feel like it would make the spell worthless.

Ideally what I want is to know what the spell can do and then be clever in working within those constraints. My character is a genius so he ought to be able to work out great ways to use his powers just as I can.  One thing I suggested to Naked Man my GM is that the spell not be able to determine people's thoughts or state of mind.  The system generally doesn't seem to assume that all gods can read everyone's mind, much less any random powerful being out there.  I think that retains plenty of power for the spell but gets rid of some of the more outrageous abuses.

The sort of power this spell represents really changes the nature of the GM's job.  Fireball is good and all, but there are answers for it.  Contact Other Plane changes the nature of the player / GM interaction in far more fundamental ways than any combat spell does, so it requires a lot of finesse and thought to adjudicate.

It is probably a lot worse when you have someone like me with the spare time to scheme up all kinds of sneaky things to ask.