In one embodiment, a first computing system receives a request from a second computing system, the request indicating an information item displayed on the second computing system. In response to the request, the first computing system determines whether the information item is associated with any call-to-action provided by any third computing system. If the information item is associated with one or more calls-to-action provided by one or more third computing systems, then the first computing system sends the one or more calls-to-action provided by the one or more third computing systems to the second computing system to be displayed on the second computing system in connection with the information item.