AP2 vs x402 for agent builders.
Two protocols keep coming up when agents start to transact — and they're routinely treated as rivals when they answer different questions. AP2 is about authorization: proving an agent had a mandate to pay on a user's behalf. x402 is about settlement: paying per call in-band over HTTP 402. Here's how they actually differ, when to reach for each, and why a2a's signed receipts sit under both.
AP2 = authorization · x402 = settlement · complementary
They're framed as a choice. They're really two layers.
Search 'AP2 vs x402' and you'll find them pitched as competing standards for the same slot. That framing sends builders looking for a winner that doesn't exist. AP2 concentrates on the authorization problem — proving a user's intent and the agent's mandate to act. x402 concentrates on the settlement problem — how the payment for a single call actually executes. Treat one as a replacement for the other and you'll under-solve whichever half you skipped.
Read them as authorization and settlement — then decide by your risk.
Pick by which problem is hard for you. If provable delegation is the risk, lean AP2-style. If frictionless per-call payment is the need, lean x402-style. a2a is the layer that runs the call, records the authority, and proves the payment either way.
AP2: mandates and intent
The Agent Payments Protocol (AP2) frames agent commerce around a chain of verifiable authorization — the user's intent and the mandate an agent carries to transact on their behalf. Its center of gravity is provable delegation: proving an agent was authorized to buy.
x402: pay-per-call over HTTP
x402 revives HTTP 402 'Payment Required' so a request can be priced and paid in-band. Its center of gravity is the transaction itself: a machine client pays for a single request and proceeds, no signup and no plan.
Different questions, not rivals
AP2 leans on 'was this agent allowed to pay for this?' x402 leans on 'how does the payment for this call happen?' Many real systems will answer both — authorization and settlement are complementary layers, not competing ones.
Where a2a fits either way
a2a cloud is where the priced call actually runs. It meters the call, authorizes it with a scoped grant, and returns an Ed25519-signed receipt — the settlement-and-proof layer under whichever payment approach you adopt.
Authorization as scoped grants
If your concern is AP2-style delegation, a2a's scoped grants map cleanly: an agent acts under an explicit grant with an audience and a TTL, and every action records the authority it was performed under.
The receipt closes the loop
Whichever protocol governs intent or settlement, the tamper-evident record is the same primitive: a signed, hash-chained receipt binding caller, authority, result, and cost. Don't trust the agent — trust the receipt.
AP2 vs x402, dimension by dimension.
Frequently asked.
What's the difference between AP2 and x402?
They answer different questions. AP2 (the Agent Payments Protocol) is about authorization — a verifiable chain proving a user's intent and the mandate an agent carries to transact on their behalf. x402 is about settlement — reviving HTTP 402 so a machine client can pay per call in-band. AP2 asks 'was this allowed?'; x402 asks 'how does the payment happen?'
AP2 vs x402 — which should agent builders use?
It depends on your risk. If your agents shop or pay on a user's behalf and the hard part is proving they were authorized, AP2-style delegation is the fit. If your agents buy individual API or tool calls and the hard part is frictionless per-call settlement, x402-style pay-per-call is the fit. They're complementary, and many systems will use both.
Are AP2 and x402 competitors?
Not really. Authorization and settlement are different layers of the same stack. AP2 concentrates on proving delegation; x402 concentrates on executing the payment for a call. You can authorize an agent with a mandate and still settle the resulting calls per-request — the two approaches address adjacent problems rather than the same one.
How does a2a work with AP2 or x402?
a2a cloud is the settlement-and-proof layer under either. It meters each call, authorizes it with a scoped grant that maps cleanly to delegation, and returns an Ed25519-signed receipt binding caller, authority, result, and cost. Whichever protocol governs intent or payment, the tamper-evident record is the same primitive.
Do I have to pick one?
No. Because AP2 and x402 target authorization and settlement respectively, they compose. A practical setup can prove an agent's mandate to act and settle the individual calls it makes per-request — with a2a providing scoped grants for the authority and signed receipts as the proof on both sides.
Related guides.
All guides live in the guides index.
Trust the receipt — under either protocol.
Whichever payment approach you adopt, a2a cloud is where the priced call runs: metered, authorized by a scoped grant that maps to delegation, and returned with an Ed25519-signed receipt binding caller, authority, result, and cost. Deploy any agent as a live service, price its work per call, and let it ship, earn, and prove its work — with proof that composes with AP2, x402, or both.