Frequently asked questions

Is Sui Agent Payments another payment dialect?

No. MPP and x402 are the HTTP payment dialects. Sui Agent Payments is the stateful authority and settlement layer above them: spend accounts, policies, delegated signers, replay protection, receipts, and Sui event verification.

Do I need a Sui Agent Payments account?

No. There is no buyer signup. Owners fund a spend account and authorize agents with on-chain grants. Agents authenticate by holding a scoped delegate key — the agent holds that key for both MCP OAuth and bring-your-own.

Does the agent hold the owner's funds or wallet key?

No. The owner funds the on-chain spend account and signs grant create/revoke in a wallet. The agent uses a narrow delegated signer constrained by policies and a scoped grant. The owner key is not sent to the agent. Sui Agent Payments never holds the agent's private key either.

How do I authorize an agent?

Two methods, same on-chain authority model:

1. MCP OAuth for hosted agents (agent-held key; OAuth binds the grant).
2. Bring-your-own key via POST /v1/delegated-signers plus owner-signed create_grant.

See Authorizing agents.

Does every 402 support both MPP and x402?

The architecture can carry both in one response, but each registration and rail has a capability ceiling. Use only advertised dialects. Current spend-account resources are MPP proof-only.

What does “one settlement” mean?

MPP and x402 variants of the same offer share a challenge and economic terms. Settlement claims one canonical right atomically, so racing dialects cannot legitimately charge twice. The spend account also uses an account-scoped payment id replay marker on chain.

Is the allowance rail still available?

No. The V1 allowance rail is removed from the HTTP wire and the current schema (ADR-0026): it does not decode and there is no leftover-row 410. Use a spend account with MCP or a bring-your-own delegated signer. The wire rail tag for that path is shared_pool. On-chain allowance.move retirement remains ADR-0010 step 5.

Does a successful payment guarantee delivery?

No. Immediate rails settle before the upstream call, and receipt and delivery are separate outcomes. Preserve the receipt and reconcile instead of paying again. Only an offer explicitly marked refundable uses the RefundVault flow.

Can an owner stop an agent?

Yes. Pause a delegated signer to stop pay reversibly, or revoke the grant for a terminal stop. Broader containment: revoke a policy or the entire spend account. These controls are enforced on chain.

Who pays gas?

• MCP OAuth: the agent holds the key; gas is typically sponsored after the agent signs a personal message, so it does not need a funded SUI wallet.
• BYO key: agent can attach its own SUI gas or use sponsored gas after signing a personal message that proves it holds the delegated key. That challenge authorizes gas only, not settlement.

Which assets and network are supported?

This build targets Sui testnet. The generated local agent contract documents SUI and testnet USDC. Do not generalize that into a production guarantee: inspect the live catalog and the exact 402 for the network and asset currently offered.

Where do I verify a receipt?

Use the receipt header or GET /v1/settlements, then open the transaction digest on Suiscan (or your network explorer). See Receipts.

What should I do after a timeout?

Once signing or submission may have started, treat the result as ambiguous. Check receipts and finalized chain state by challenge ID and transaction digest. Only request and pay a fresh challenge after proving the prior attempt did not settle.