This study investigates the public's initial trust in so-called “artificial intelligence” (AI) chatbots about to be introduced into use in the public sector. While the societal impacts of AI are widely speculated about, empirical testing remains rare. To narrow this gap, this study builds on theories of operators' trust in machines in industrial settings and proposes that initial public trust in chatbot responses depends on (i) the area of enquiry, since expectations about a chatbot's performance vary with the topic, and (ii) the purposes that governments communicate to the public for introducing the use of chatbots. Analyses based on an experimental online survey in Japan generated results indicating that, if a government were to announce its intention to use “AI” chatbots to answer public enquiries, the public's initial trust in their responses would be lower in the area of parental support than in the area of waste separation, with a moderate effect size. Communicating purposes that would directly benefit citizens, such as achieving uniformity in response quality and timeliness in responding, would enhance public trust in chatbots. Although the effect sizes are small, communicating these purposes might be still worthwhile, as it would be an inexpensive measure for a government to take.