Users are increasingly accessing the Internet from mobile devices as well as conventional desktop computers. However, it is not reasonable to expect content authors to create different data presentations for each device type, but the content source should be reused across multiple delivery contexts whenever possible. The objective of this research is to develop a supporting tool for the presentation customization that follows after the content specialization in device-independent authoring. This paper presents a tool that automatically generates content customization metadata on the basis of users’ editing operations toward the desired results of the customization. A prototype of the metadata generator was developed for the generation of page-clipping annotations to be used for an annotation-based transcoding system.