Curse of Knowledge

If

Once you know a thing, you cannot easily imagine not knowing it. Engineers write docs, error messages, and APIs that are obvious to themselves and opaque to the next person who has to use them.

Then

Before shipping documentation or a public API, have someone who has never touched the system attempt the task while you watch silently. Their confusion points exactly at the assumptions you forgot to spell out.

Unless

User Testing / Onboarding Buddies / Documentation Reviewers Outside the Author's Team