A method implemented by one or more processors, comprising: receiving, by one or more of the processors, a selection of a selectable element at a graphical user interface rendered by a first application of a computing device, wherein the first application is not an automated assistant application and the selectable element is configured to cause an automated assistant application that is separate from the first application to invoke an agent associated with the graphical user interface, the selectable element being associated with a uniform resource locator, URL, wherein the URL identifies the agent, an action to be performed by the agent, and one or more specified values for performing the action, the one or more specified values provided by a user to the first application before selection of the selectable element, wherein the URL further identifies a modality of dialog with the automated assistant, wherein the modality is one of voice or text; in response to the selection of the selectable element, invoking (506, 508), by one or more of the processors, the agent via the automated assistant application, the agent being one of a plurality of available agents that can be invoked via the automated assistant application which is configured to perform one or more actions associated with the first application; receiving, by one or more of the processors, responsive content from the agent in response to invoking the agent; and outputting, by one or more of the processors, an output provided by the automated assistant application via an automated assistant interface, that is based on the responsive content received from the agent. receiving, by one or more of the processors, a selection of a selectable element at a graphical user interface rendered by a first application of a computing device, wherein the first application is not an automated assistant application and the selectable element is configured to cause an automated assistant application that is separate from the first application to invoke an agent associated with the graphical user interface, the selectable element being associated with a uniform resource locator, URL, wherein the URL identifies the agent, an action to be performed by the agent, and one or more specified values for performing the action, the one or more specified values provided by a user to the first application before selection of the selectable element, wherein the URL further identifies a modality of dialog with the automated assistant, wherein the modality is one of voice or text; in response to the selection of the selectable element, invoking (506, 508), by one or more of the processors, the agent via the automated assistant application, the agent being one of a plurality of available agents that can be invoked via the automated assistant application which is configured to perform one or more actions associated with the first application; receiving, by one or more of the processors, responsive content from the agent in response to invoking the agent; and outputting, by one or more of the processors, an output provided by the automated assistant application via an automated assistant interface, that is based on the responsive content received from the agent.