In my Agent Protocols - MCP, A2A, A2UI, AG-UI post back in March, I provided a high-level overview of the main agent protocols for tool use (MCP), agent-to-agent communication (A2A), and agent-to-UI interactions (AG-UI and A2UI).
Recently, I had a chance to explore two newer protocols focused on agentic commerce and payments: the Universal Commerce Protocol (UCP) and the Agent Payments Protocol (AP2). Traditional e-commerce and payment flows assume a human is directly browsing a website and clicking “Buy” on a trusted checkout screen. When an AI agent shops and pays on your behalf, both the commerce workflow and the cryptographic proof of user authorization need a standard language.
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