A Leprechaun? Well you always had a significant drop of Irish blood in you.
"You will become a fairy cobbler, making or mending shoes for magical and mythical creatures." the note continues. "You will also be required to guard a crock of gold, and are under obligement to grant 1 wish per coin to any mortal who manages to get hold of any of it.
There is no height maximum for the job, but for convinience we suggest you be shrunk to a height of 3 feet.
Apply at the ring of shamrock by the old oak in the park."