When evaluating RFID library gates, prioritize detection width, which typically ranges from 90cm to 120cm per lane to ensure ADA compliance and smooth traffic flow. Ensure the system supports ISO 15693 and ISO 18000-3 protocols for high-frequency (HF) tags, which are the industry standard for libraries. Additionally, look for multi-item detection capabilities to prevent 'collision' when multiple books pass through simultaneously, and verify that the gate includes AFI (Application Family Identifier) or EAS (Electronic Article Surveillance) security bit switching for reliable alarm triggering.