<p>In modern manufacturing, seamless interaction between operators and machines is critical to efficiency and flexibility. Augmented reality instructions have emerged as an intuitive way to provide real-time guidance, reducing errors and improving productivity. However, traditional AR-based instruction systems face several challenges, including high development and maintenance costs, limited flexibility in accommodating new equipment, and unidirectional interaction that restricts real-time operator feedback. This paper proposes a bi-directional augmented reality instruction system utilizing the Asset Administration Shell to enhance adaptability and scalability in heterogeneous industrial environments. The proposed system integrates standardized instruction representation and neutral communication protocol, allowing real-time data exchange between physical machines and AR interfaces while maintaining a standardized and modular structure. By separating AR content from application programming, the system enables instruction updates and modifications without requiring software redevelopment. Additionally, bidirectional communication allows operators to not only receive instructions but also modify machine parameters directly through the AR interface. To validate the proposed approach, the system was implemented on two machine tools with distinct configurations. Experimental results demonstrated that AR instruction development efforts were reduced by over 70%, while real-time machine control through the AR interface significantly improved operational efficiency. The proposed framework enables cost-effective and flexible AR instruction systems, making it particularly suitable for small and medium-sized enterprises facing resource constraints and diverse equipment environments.</p>