  Effort estimation is an integral part of activities planning in Agile
iterative development. An Agile team estimates the effort of a task based on
the available information which is usually conveyed through documentation.
However, as documentation has a lower priority in Agile, little is known about
how documentation effort can be optimized while achieving accurate estimation.
Hence, to help practitioners achieve just-enough documentation for effort
estimation, we investigated the different types of documented information that
practitioners considered useful for effort estimation. We conducted a survey
study with 121 Agile practitioners across 25 countries. Our survey results
showed that (1) despite the lower priority of documentation in Agile practices,
98% of the respondents considered documented information moderately to
extremely important when estimating effort, (2) 73% of them reported that they
would re-estimate a task when the documented information was changed, and (3)
functional requirements, user stories, definition of done, UI wireframes,
acceptance criteria, and task dependencies were ranked as the most useful types
of documented information for effort estimation. Nevertheless, many respondents
reported that these useful types of documented information were occasionally
changing or missing. Based on our study results, we provide recommendations for
agile practitioners on how effort estimation can be improved by focusing on
just-enough documentation.
