As I understand it, if a magnet sticks to the base it is probably just fine. It works by generating currents by applying a magnetic / electric field, and that heats up the pot or pan.
So would, for instance a stainless steel, stove top kettle be suitable if it didn't have a flat bottom ?.
Aside from that, dose the quality of the steel have any bearing on it ?.
If your kettle doesn't have a flat bottom, it is going to take an age to boil as only a limited amount of the surface area is going to be making contact.