When sourcing Miniature Circuit Breakers (MCBs), you must prioritize the Rated Breaking Capacity (Icn), typically ranging from 6kA to 10kA for standard commercial use. Ensure the Tripping Characteristics (Curve B, C, or D) align with your load type: Curve B for resistive loads, Curve C for general inductive loads like motors, and Curve D for high inrush current equipment. Additionally, verify the Mechanical and Electrical Endurance, aiming for at least 20,000 and 10,000 operations respectively to ensure long-term reliability.