Good source code documentation, especially of programming interfaces, is essential for using and maintaining software components. In this paper, we present the Quasoledo tool that automatically measures the quality of documentation with respect to completeness, quantity, and readability. We applied our set of metrics to the Eclipse project, and benchmarked against the well-documented Java class library. The result of Quasoledo is a map of documentation quality in Eclipse, showing the best documentation for its core components. Additionally, we looked at the evolution of Eclipse and identified batch updates that caused jumps in documentation quality. For Eclipse, only 32.6% of all changes touched documentation.