A2A
An open protocol aimed at capability discovery, task delegation and interaction between independent agents. It addresses a different layer from MCP, which focuses on tool/resource access.
Why it matters
Agentic commerce combines model reasoning with deterministic transaction systems. Tool access, commerce state, payment authorization and user intent are not the same thing; each layer needs explicit boundaries and an authority model.
What does it look like in practice?
A travel agent may use MCP or provider APIs for capabilities, prepare checkout through a commerce contract such as UCP/ACP, and involve separate authorization/payment layers such as AP2, MPP or x402. These protocols do not solve the same problem.
Implementation questions
- Which capabilities can the agent access?
- What action and amount did the user explicitly authorize?
- Is transaction state held in a deterministic system independent of the model?
- Where are audit trails and human-approval checkpoints?
Common mistakes
- Treating an LLM decision as payment authorization
- Equating tool access with purchase authority
- Treating protocol names as one interchangeable agentic-commerce standard
Where does it appear in the travel stack?
A2A commonly appears across agentic layers. Its implementation should make source-of-truth, identity, freshness and transaction-ownership boundaries explicit.