Tando enhanced mypy’s error reporting by refining how callable expressions are formatted in type error messages. Working in the python/mypy repository, Tando implemented logic to selectively apply pretty_callable formatting, ensuring complex callable signatures are displayed more readably while simple positional-argument callables retain concise output. This targeted approach addressed user-reported edge cases and reduced confusion during debugging. Using Python and leveraging skills in code formatting and type checking, Tando’s work improved the developer experience by making error messages clearer and more actionable. The changes demonstrated thoughtful attention to usability and maintainability, focusing on practical improvements rather than broad architectural changes.