A2A (Agent-to-Agent Protocol)
Also known as: Agent-to-Agent
Protocol for agent-to-agent communication — how one AI agent hands off, negotiates, or coordinates with another. Enables multi-agent commerce flows (e.g., a shopping agent talking to a fulfillment agent).
A2A is the Agent-to-Agent protocol family. Where ACP defines shopper-to-agent commerce, A2A defines agent-to-agent — the machine-to-machine layer where a shopping agent might hand off to a fulfillment agent, a customer-service agent, or a returns-processing agent.
A2A becomes important as multi-agent commerce flows mature. A shopper asks Claude for a bag; Claude confers with the brand's authorized product agent (via A2A) to confirm availability, warranty terms, and shipping options; the brand agent then completes the transaction via ACP or UCP. All happens in seconds, invisibly to the shopper.
For merchants today, A2A is largely a future-oriented layer. But agentic commerce platforms that abstract protocol translation increasingly expose A2A endpoints so merchant agents can participate in multi-agent flows without direct engineering work.
See also
MCP (Model Context Protocol)
Anthropic-authored open standard for connecting AI assistants to external data sources, tools, and services. Widely adopted across AI vendors; foundation for tool-use-based commerce.
ACP (Agentic Commerce Protocol)
OpenAI + Stripe's open protocol for agent-initiated commerce. Powers ChatGPT Instant Checkout and Copilot-adjacent commerce. Enables in-conversation purchase completion without the shopper leaving the agent.
UCP (Universal Commerce Protocol)
Google + Shopify + retail-consortium open protocol for agent commerce, endorsed at NRF 2026 by 20+ retailers including Walmart, Target, Wayfair, Etsy, and (as of Q1 2026) Amazon.