i have kept white's and firebelly toads together in a large paludarium with no issues. there might be plenty of reasons why some will not do so, but it can be done. i did water changes often to keep any potential toxins down.
I know some will disagree with me--on each end of this issue. I do not keep White's with anything small, and not necessarily cause I fear predation. I have found that well-fed White's (like some lizards) if raised from babies will stick with insects. Conversely, I find that White's that are fed the weekly pinky tend to be more, shall we say, "gustatory" (nice way of saying predatory). In other words, they're not Cuban tee frogs, which would eat you if they could. Of course, any carnivore would eat a smaller organism if hungry enough.
I would certainly not dis keeping White's with say, tree skinks or Phelsuma grandis in a big, vertically oriented set up. That said, 24 years ago I saw a White's jump down and grab a cricket sticking out of a small Bombina's mouth. Instinctive feeding reflex kicked in, and the White's started to swallow the cricket and the attached frog. I reached in and pulled them apart--and the White's was dead in less than an hour (which is why to this day I will not keep Bombinas with any tree frogs or lizards).
I would set up the toad in a different tank. Besides, one is arboreal and the other terrestrial, with different set up requirements.