The description should explain what the error was, followed by the why it occurred. Information that is useful for debugging should be included with errors where possible in a "Details" section. You should also avoid making the text unnecessarily wide. e.g.
❌ Figure: Bad Example - A message box that does not intuitively alert the user
This is confusing, because it uses different terminology to the title ("estimate" instead of "quote")
There is no punctuation
The word "Error" is meaningless
Line breaks are not present, so the message box is too wide and the text may wrap in the wrong spot
✅ Figure: Good Example - A message box that is clear, consistent and intuitive
Terminology is consistent
Punctuation is present
"Details" indicates that this information is useful for debugging
The text is split across three lines, and the technical information after Details is separated from the description of the error