While conversational agents (CAs) become increasingly technologically advanced, users struggle to effectively navigate their capabilities. Onboarding, a process of familiarization and introduction, can be leveraged to provide critical information and help users assess, engage, and collaborate with CAs. Thereto, we survey users’ information needs and derive an Onboarding Framework to guide the design of such initial interactions (study 1), consisting of three themes (Capabilities and Limitations, Disclosures and Validations, Guidance and Contestability) and 12 subthemes. Moreover, we explore users’ willingness to engage in onboarding and its impact on satisfaction, ease of use, trust, and CA perceptions (study 2). We find that 85% engage in onboarding and that the depth of the onboarding significantly influences ease of use, whereas breadth, the diversity of explored themes, is significant for trust and CA perceptions. Both depth and breadth influence satisfaction. Our findings establish onboarding as a critical phase in CA interactions.