I'm thinking I could take it two ways:
Either he's a prankster and though at first he'll get you what you want within reason, eventually he'll start tampering with whatever it is he's brought you; a cockroach in your sandwich for instance or ice cubes made of urine in your tasty cold beverage.
and/or:
He constatly gripes about having to do anything for anyone and will talk to anyone he can find while he's out and around about it, and he's a lazy bum who takes his time or "forgets" what he was doing and has to repeatedly be reminded, along the lines of what LeBlueDude suggested.
I dunno though, I want to keep it simple and short, and it's already a bit lengthy.
I thought of him as a kind of modern version of a genie in a bottle, but flawed in such a way that he certainly couldn't do the kinds of things a genie could, but could keep someone reasonably satisfied. He was "created" or "bound" for the sole purpose of serving whoever it was the bell was buried with and they never intended anyone else to ever use it, hence the "Forever Mine" bit. It's just a coincidence that the bell was found and acquired by the Foundation.
I've been super busy the past few days, I'll update it with some of these ideas this weekend if any of them sound appealing. I'm thinking further interviews and test logs will reveal his darker side over time while I leave the main body of the page intact. Keep the critiques coming!