Not the Book by Phillip Pullman

Just sayin'.

Is this the world's shortest fairy tale?  The Grimms' The Golden Key is reproduced here in full for your enjoyment, translated by D.L. Ashliman.

Once in the wintertime when the snow was very deep, a poor boy had to go out and fetch wood on a sled.  After he had gathered it together and loaded it, he did not want to go straight home, because he was so frozen, but instead to make a fire and warm himself a little first.  So he scraped the snow away, and while he was thus clearing the ground he found a small golden key.  Now he believed that where there was a key, there must also be a lock, so he dug in the ground and found a little iron chest.  "If only the key fits!" he thought.  "Certainly there are valuable things in the chest."  He looked, but there was no keyhole.  Finally he found one, but so small that it could scarcely be seen.  He tried the key, and fortunately it fitted.  Then he turned it once, and now we must wait until he has finished unlocking it and has opened the lid.  Then we shall find out what kind of wonderful things there were in the little chest.

This needs no other commentary than this: it was historically always placed as the last tale in the collection.