A robotic system that efficiently uses water and pesticides for tomato cultivation is not widely available in sustainable agriculture practice. This study proposes a design for a new AI-powered robot that automates pesticide and irrigation applications on small- to medium-sized tomato farms. The system operates based on water and pesticide requirements, turning on weekly to follow a predefined zigzag path in the field to reach every plant. The robot uses ultrasonic sensors and small reflective markers on the plant support sticks to accurately identify each tomato plant. The system then takes a picture of the plant and runs the data through a pretrained YOLOv8-based disease classifier, which helps find plants that need treatment. The robot skips plants that are healthy, which saves pesticides, resources, and the environment. The robot sprays pesticides on the affected area and, simultaneously, applies irrigation water. The irrigation water demand is calculated based on crop water needs and the amount of water that evaporates from the air, ensuring efficient water use. The system hasn’t been tested in the field yet, but an early estimate of the development cost is USD 300, suggesting a low initial price for small- to medium-sized farms. The combination of plant-level monitoring, selective treatment, and combined irrigation will help lower input costs, have less impact on the environment, and enable farmers to use more sustainable methods.