So the categorization of toxins vs. nutrients is just "bio-active molecules which are either detrimental or beneficial" to the organism?

Or do nutrients always have to transfer solar energy as some post above alludes to? Vitamins functionally support the organism without delivering energy - but they are considered as nutrients too.

Or are we going to include the criticality of its absence? The absence of vitamin C causes scurvy. The absence of caffeine merely means losing luxury benefits "on top of" what we strictly need.

In that way and as the benefits seem to outweigh the negatives, one could definitely argue that caffeine is a nutrient.