In writing there is a number of unofficial "tests" such as "the Bechdel test". As with most things, people start to add to that kind of stuff and eventually you end up with something like the Flying Spaghetti Monster.
That aside, I found an interesting test that could be applied to magic. It's called The Sexy Lamp Test. It goes a little something like this:
"I’ve got another test that works just as well. The Sexy Lamp test. If you can take out a female character and replace her with a sexy lamp, YOU’RE A FUCKING HACK.” - Kelly Sue DeConnick
Taken into context for magic, if your magic assistant could be replaced by a sexy table, you might want to rethink how much you are paying that person because they are essentially a prop.
You wouldn't have to pay this as much to do the show.
There is so much great dynamic by-play that can be achieved by adding a second person to the act so why waste that by just using them to steal things from or ditch onto?
So take a step back and either start writing or head out to your local Ikea. Your call.