A software facility allows custom components to be created and used in an end user application, such as a workflow application that defines business processes or a graphical design application. The facility provides a custom component definition that includes an indication of criteria for custom components for use in the end user application. A designer of the custom component provides the software facility with an indication of functionality for the custom component, wherein the indication satisfies the criteria for custom components included in the provided definition. The custom component is registered with the end-user application. This registration enables the end user application to access the custom component from within the end user application without the use of programming scripts to call the customized component from outside of the end user application.