The present invention is an action agent architecture in a scalable multi-service virtual assistant platform that can construct a fluid and dynamic dialogue by assembling responses to end user utterances from two kinds of agents, information agents and action agents. The virtual assistant platform comprises a plurality of action agents to perform two or more actions in response to parsed user input, contextual data, and/or an information value obtained from an information agent. The plurality of action agents are interrelated via at least one follow-up connection which interrelates any two of the action agents such that a second action agent follows-up with a second action after a first action agent completes a first action based on a trigger condition. The second action agent utilizes at least one information value set by the first action agent or a system state change triggered by the first action agent.