Artificial intelligence (AI) tools such as recommendation engines, chatbots and virtual assistants are increasingly embedded in online retail platforms, reshaping how consumers search, evaluate and purchase products (Riegger & Hoffmann, 2026; Kiran & Aithal, 2025). Drawing on the Technology Acceptance Model (TAM) and AI-specific extensions, this study examines how the perceived usefulness of AI tools influences online buying behaviour among consumers in Chennai, India. A structured questionnaire was administered to 300 online shoppers who have used AI-enabled features such as personalised recommendations, conversational agents and visual search. Data were analysed using descriptive statistics, reliability analysis, exploratory factor analysis, correlation, multiple regression, ANOVA, chi-square tests and structural equation modelling. The conceptual model posits that perceived usefulness significantly predicts online buying behaviour, with perceived ease of use and trust in AI tools acting as complementary drivers. The study contributes a city-level perspective from an emerging economy and offers practical implications for e commerce firms seeking to design consumer centric AI interfaces.