One of the things that wonder me when looking at source code of Agile projects, is the lack of documentation. The minimal amount of documentation on classes/interfaces is the description of its core responsibility: what is the purpose of this class? It doesn’t need be be very long; a few sentences would be enough. And if the class/interface is part of some design pattern, this should be added to the documentation as well. If the the class is completely self contained, and the pattern is well known (like a Strategy or Decorator), I could live without the documentation but not everyone is a pattern freak, I would rather see it in the documentation.
Another important document is some sort of architectural overview to get a quick understanding of the system without needing to browse through all sources. This document should at least cover the main components of the system, what the responsibilities are of these components and how they interact and why this approach is being used. Without this information it is very hard to say anything about performance, security, scalability, re-usability.
I know that not writing documentation shouldn’t be blamed on the Agile methodology, but on its misinterpretation.
If you want to remove redundant parts in the documentation, why is the @author tag not removed from the javadoc? If I want to figure out who wrote it (or changed it) I could look at the blame functionality most version control systems provide.