A chatbot may be invoked in an online communication session between two or more human users to share additional content in the communication session. To determine when to invoke the chatbot, e.g., at which point during their conversation, an interaction model may be trained on past conversation data between participants to determine so-termed interaction points in the past conversation data which are predictive of a subsequent sharing of additional content by one of the participants. Having generated the interaction model, the interaction model may be applied to an online communication session to detect such interaction points in a real-time or near real-time conversation between users and to invoke the chatbot to participate in the communication session in response to a detection.