> Best match is versatile which usually means: Capable of many different uses

with "multi-purpose", "adaptable", "flexible" and "multi-use" as the runner-up candidates.

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Like you, I had no idea that tools like OneLook Thesaurus existed (despite how easy it would be to make one), so here's my attempt to look this up manually.

"Admitting a large number of uses" -> manually abbreviated to "very useful" -> https://en.wiktionary.org/wiki/useful -> dead end. Give up, use a thesaurus.

https://www.wordhippo.com/what-is/another-word-for/very_usef..., sense 2 "Usable in multiple ways", lists:

> useful multipurpose versatile flexible multifunction adaptable all-around all-purpose all-round multiuse multifaceted extremely useful one-size-fits-all universal protean general general-purpose […]

Taking advantage of the fact my passive vocabulary is greater than my active vocabulary: no, no, yes. (I've spuriously rejected "multipurpose" – a decent synonym of "versatile [tool]" – but that doesn't matter.) I'm pretty sure WordHippo is machine-generated from some corpus, and a lot of these words don't mean "very useful", but they're good at playing the SEO game, and I'm lazy. Once we have versatile, we can put that into an actual thesaurus: https://dictionary.cambridge.org/thesaurus/versatile. But none of those really have the same sense as "versatile" in the context I'm thinking of (except perhaps "adaptable"), so if I were writing something, I'd go with "versatile".

Total time taken: 15 seconds. And I'm confident that the answer is correct.

By the way, I'm not finding "multifarious" anywhere. It's not a word I'm familiar with, but that doesn't actually seem to be a proper synonym (according to Wiktionary, at least: https://en.wiktionary.org/wiki/Thesaurus:heterogeneous). There are certainly contexts where you could use this word in place of "versatile" (e.g. "versatile skill-set" → "multifarious skill-set"), but I criticise WordHippo for far less dubious synonym suggestions.