error handling in existing system

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I want to add error messages to an existing system, the problem is that there is no designated space for them

How do you suggest to handle errors?

What I plan to do:

  • Paint the frame in red
  • Add a small X on the top right of the frame (for accessibility)
  • show the error on tooltip

Questions

  • Will there be an accessibility problem for screen readers to handle popover or tooltips?
  • Any other ideas on how to display errors when you dont have enough space?