Use Cases for Adding an Action Extension You can extend the vSphere Web Client by adding actions associated with an existing type of vSphere object, or with a new type of vSphere object. You might add actions to an existing object type if you have created a custom version of that vSphere object, such as a custom host. In addition to creating the action extension in the user interface layer, you must also add a Java service to the vSphere Web Client service layer. This Java service is used to perform the action operation on the target vSphere object.