I call this read-through documentation (a la caching), in that you're always reading from the documentation (cache) and a missing document pulls it into the documentation (by writing it), before servicing the request.
It takes discipline, as otherwise everyone skips the "write documentation" step, and it will annoy some people with high priority issues.
But IMHO, it's the only thing that actually scales if you truly want comprehensive, continuously-updated documentation.
Side note: An excellent way to generate drafts for missing content is have your new hires write them as they get up to speed. By definition they're looking everything up, so they'll notice gaps. And they have time, before they're fully up to speed. And as long as someone with knowledge proofs their draft, their lack of experience shouldn't matter.
It takes discipline, as otherwise everyone skips the "write documentation" step, and it will annoy some people with high priority issues.
But IMHO, it's the only thing that actually scales if you truly want comprehensive, continuously-updated documentation.
Side note: An excellent way to generate drafts for missing content is have your new hires write them as they get up to speed. By definition they're looking everything up, so they'll notice gaps. And they have time, before they're fully up to speed. And as long as someone with knowledge proofs their draft, their lack of experience shouldn't matter.