If a developer cannot find how to use your API, your API does not exist for them. Documentation is not an afterthought of engineering, it is the surface through which most of your users meet your work.
Write Docs Before Code
Drafting the docs forces clarity on the contract before the implementation calcifies bad decisions.
Examples Are Mandatory
No one reads reference pages cold. Show the happy path in five lines and most developers will figure out the rest.
Keep It Honest
Outdated docs are worse than missing docs. A broken example trains your audience to distrust everything else.
Measure It
Search queries that return nothing, support tickets that quote the docs, pages with high bounce rates. Treat these as bug reports.
Conclusion
Good docs are how a developer falls in love with a product. Bad docs are how they quietly leave.