Agent Payment Protocols Race: A Comparative Analysis of x402, AP2, MPP, and ACP

Fireblocks has released a report comparing four mainstream AI agent payment protocols: x402, AP2, MPP, and ACP. x402, based on the HTTP 402 status code and championed by Coinbase, emphasizes compatibility with existing web infrastructure. AP2, introduced by Visa, focuses on merchant acceptance and settlement workflows. MPP, developed by PayPal, leverages its established payment network, while ACP targets cross-border settlement scenarios. The report notes that these protocols differ in authorization mechanisms, settlement speed, and compliance support, with no unified standard yet in place. As AI agents increasingly execute transactions autonomously, protocol choice will significantly impact the security and efficiency of machine-to-machine payments. Fireblocks advises enterprises to evaluate protocol compatibility based on their specific business use cases, while also paying close attention to compliance requirements such as pre-settlement firewalls and Know Your Agent (KYA) protocols.