||Java Tool platforms offer a new way of application development. Applications can be built by implementing modules, which plug into the tool platform. The functionality is not only implemented in pure Java bytecode, but also declaratively in XML. The module programmer benefits from platform services, like module versioning and module dependency checks. Programmers implement their modules against interfaces of a tool platform’s core modules or self written modules. In this paper, we describe the differences between tool platforms and traditional application frameworks. We compare two popular tool platforms for Java application development, NetBeans and Eclipse, and we offer a guide when to choose which platform.