The magical advice canary (MAC) is a canary that travels with the party and offers advice by whispering in people's ears. But really, it is a literary device meant to speed up the plot when players attack gazebos.
For example, now the DM can say that the MAC whispers
"Hey, let's go to the caves!"
rather than the DM directly saying:
"Guys, there's nothing interesting in the town -- the adventure starts when you go to the caves!"
The MAC is really some kind of avatar of a helpful spirit. The MAC is magic in that:
A few ideas:
The party does a good deed for an NPC, and the MAC was previously paired with the NPC. While the NPC is thanking the party, The MAC flits around the NPC.
The NPC explains what the MAC is and then tells the party that the MAC wants to go with them. This makes the most sense if the MAC is going to be mostly helpful and not too mischievious or self-centered.
The MAC can be a prize in some carnival. "Win an amazing
Maybe an old wizard tricks the party into feeding the MAC while it is in its cage. And maybe once you feed it, it is hard to get rid of. This makes more sense if the MAC is mischievious.
It won't answer stuff like "hey, does that treasure chest have a trap?". Or maybe it will, but the answer will be something like: "Only one way to find out!"
Again, the goal here is to give the DM an in-game means of driving the plot and making the game more fun, not giving the players a way to skip thinking things through.
Maybe!
The MAC is here in the world to have a good time. So if that means messing with the party as they keep trying to kill it, then go with it.
It could be entertaining to watch players come up with elaborate ways to destroy the MAC and still have it show up the next day.
Maybe damage done to the MAC actually ends up harming somebody else in the party. That could be a fun thing to find out in-game.
Maybe the avatar is a crow. Or a snake.
Or a bitchy walrus that the party has to haul around in a cart. And she only talks when presented with a fish to eat. And the fish is never quite as good as this one fish that the walrus had a few centuries ago.
Or the avatar is a goldfish that lives in a goldfish bowl, and it talks by making bubbles in special patterns. So it comes with a book that explains how to read the patterns.
Or it is a spider that that will spin a web with clues written in it.
Or it could be a donkey that taps out stuff with his hooves.
If the avatar isn't very portable, then it might not be so easy to use it to hint that the party is wasting time. But that could be fun for other reasons.
Maybe the MAC has its own agenda beyond just being nice, for example: