I think that's what the Omniscience Index is for:

https://artificialanalysis.ai/evaluations/omniscience#aa-omn...

It rewards correct answers and penalizes hallucinations, and finally no reward for refusing to answer.

It's interesting just how poorly some popular Chinese models fare in this regard, like GLM 5.1 or DeepSeek 4 Pro.

Gemini 3.x has truly remarkable knowledge given how it leads in this benchmark despite being (quite a bit) more prone to hallucinate than Claude Opus.