How to eject minidisc from MBP
Ah, the downfall of slot drives - getting a disc stuck in it when it dies :(

As per the comment to your question, I presume that this is a smaller CD, not an actual minidisc that is more akin to a floppy disk in a plastic case?

Oddly, some slot loading mechanisms can support these smaller discs.  For example, the Nintendo Wii is a vertical slot loader that will accept Gamecube discs that are smaller than regular CDs/DVDs.

Obviously, the MacBook won't tho.  I would recommend the use of a pair of slim "shims" that you can use to make a pair of tweezers with.  They would need to be both slim, but strong enough to get a grip with.  You may need to cover the ends if you don't want to risk scratching the disc.

Alternatively, a piece of double sided sticky tape on the end of a plastic ruler may help.  Just insert an inch (don't go too far, don't want to touch the laser with sticky stuff), and wobble it up and down a bit, see if you can get contact with the edge of the disc, then slowly pull it out.  If this is tricky, try it with the drive/laptop upside down.