In my experience, all thesauri suck, either having far too few quasi-synonyms (and thesauri that divide them into closeness tiers aren't very useful in practice

In my experience, all thesauri suck, either having far too few quasi-synonyms (and thesauri that divide them into closeness tiers aren't very useful in practice), or having far too many quasi-synonyms without distinguishing senses or parts of speech (sometimes, but only sometimes, intersection search works to avoid this), or both. As for antonyms, good luck finding anything at all. So, using additional tools, even if not designed for the task, is often useful.