So it seems that poison and venom both have their own tags, though the poisons tag is widely more popular, even regarding situations where where a venom tag would be more appropriate.
In biological contexts, "poisons" are chemicals produced by a living organism to harm animals that eat or touch them, while "venoms" are harmful chemicals delivered through injections, like bites or stings. In a non-biological context, though, these terms are typically used interchangeably; the definition of the poisons tag (which matches the broad definition on the Wikipedia page for "Poison") includes any chemical substances harmful to living organisms, whether they are produced through biological or non-biological means.
Should we encourage correct use of the terms when appropriate? Or is the inclusion of the venom tag needlessly pedantic?