Tool that married code with documentation

Nearly all tools product and eng teams use today are web-based. Documentation lives outside of the context where it’s implemented, i.e., code.

Think about technical specs, product specs, product architecture docs and so forth. They get outdated pretty quickly as the team starts writing code (things change). The context also lives completely outside and divorced from the source of truth in code. I’ve worked in a number of teams over the years where the technical specs are horribly outdated and there’s almost no point reading them to get an understanding of how something works.

I’ve been thinking of building a tool that enables developers to create documentation that is accessible to everyone, but from within code. The main problem it solves is linking documentation to actual implementation details. This is often very useful when debugging something, helping non-dev folks to learn about context or decisions or when on-boarding new developers. But more importantly, it would mean fewer docs are out of date. They’re front and center in a place where engineers spend a large portion of their day.

Side note: i’m not talking of api docs or reference docs.

Do you see value in this? Does something like it already exist?