Answer: disabled is a waiting state

A frontend answer that frames disabled controls as waiting states with visible missing conditions.

I would treat disabled controls as waiting states, not as errors. That changes the copy: - error: "Email is invalid" - waiting state: "Enter a valid email to invite" The second version is closer to what the user needs. It says what condition would unlock the action. It also avoids making the page feel hostile before the user has submitted anything. For repeated controls, the reason can be a tooltip or helper text. For a primary action, I would keep the reason visible near the button. If the button is important enough to block progress, the missing condition is important enough to show.