If the automation trigger "Manual trigger from work item" is enabled, users can manually run automation rule from work item.
Also, if the "Prompt for input when this rule is triggered" is enabled for this trigger, users can enter the input for the rule.

For that case, the fixed text "Your input is required to complete this action" is displayed in the manual trigger modal.
It would be better if there is an ability to customize this text in order to admins can specify the instruction when executing that rule.