Virtual personal assistants are artificial intelligence systems that perform tasks on a computing device in response to natural-language requests from a user. Typical virtual personal assistants are monolithic applications that handle a finite set of tasks for the user, such as calendaring, reminders, and messaging. Those virtual personal assistants understand how to respond to a number of natural language phrases associated with those tasks. Extending the capabilities of virtual personal assistants generally requires extensive modifications to analyze and respond to natural language relating to the new capabilities. For example, systems based on a grammar model must be substantially changed for any new vocabulary or phrasing behavior. Similarly, systems based on a dictation model may require extensive effort to integrate required training sets of spoken data. The effort and/or amount of data required to integrate new capabilities may increase exponentially as additional capabilities are added.