As the rate of 'hallucinations' seems to have dropped dramatically (at least IME as regards non-existent flags and the like), I'm more concerned with usage. I often use grep.app/GH code search to look for usage examples as a sanity check when things look "off", for exactly the reason you described--there's often a total lack of good documentation on things like that, especially on "younger" tools/stuff.

Most established projects has quite good documentation. And if they don’t, that’s because they consider the code as the documentation and just provide with an overview. The source code is the main truth and there’s a trick to reading it quickly. But that’s acquired by playing around with a lot of projects