A
Agent
Two uses on Atum: (1) software acting for a principal — see Know Your Agent; (2) a settlement operator’s software that fulfills payments — see Operating a settler agent.Atum ID
Identification system on the Atum network: signed credentials attached to a payment or quote so participants can be recognized without Atum assigning you an account number. Atum issues Known to Atum to participants today. See What is Atum ID?.Atomic units
The smallest indivisible amount of a token. USDC uses 6 decimals, so1000000 atomic units = 1.00 USDC. See Corridors and assets.
atum-escrow
The x402 payment scheme Atum implements: the payer funds a payment in any supported asset, on any supported chain, and the merchant receives its chosen asset on its chosen destination chain, with Atum converting between them. See Facilitated payments (x402).Auction
See Quote selection.Auto accept
An option on a payment (auto_accept) that makes the gateway select the first valid price quote at or under max_source_amount, instead of waiting for the quote window to close. See Deadlines.
Award deadline
See Quote expiry.C
CAIP-19
Chain Agnostic Improvement Proposal 19. Standard string format for identifying a specific token on a specific rail, e.g.eip155:421614/erc20:0x75faf1…. See Corridors and assets.
CAIP-2
Chain Agnostic Improvement Proposal 2. Rail identifier prefix used in CAIP-19, e.g.eip155:421614 for Arbitrum Sepolia. See Supported networks.
Confirmation
How deep a destination-chain transfer is in the chain before Atum will treat it as delivered enough to sign a release. On EVM and Tron this is a block count (min_confirmations: 1 means the including block is enough), and on chains judged by finalized the block must also be final. On Solana it is a cluster commitment (confirmed or finalized), not a count. It is not a second API call. See Confirmations.
Corridor
A source asset → destination asset pair for a payment. See Corridors and assets.Counterparty
The receiving side of a payment — merchant, wallet, or institution. See Network participants.Credential (identity)
A signed statement about a participant (a verifiable credential), presented with a payment or quote. Distinct from a payment credential. See Credentials.Credential (payment credential)
A self-contained, signed payment authorization: it carries the payer’s chosen payment terms plus the signature that authorizes the funds, so a resource server can verify and settle it without the payer being online. Both x402 and MPP send it in anAuthorization: Payment (or PAYMENT-SIGNATURE) header on the retried request. The term comes from the x402 spec’s “payment-as-credential” — read it as signed payment, not a login/API credential or an identity credential. See Payment protocols.
Credential type
The kind of identity credential: what was attested, not who the participant is — for example Known to Atum, the type Atum issues today. See Credentials and Policy enforcement.D
Decline reason
Why one settlement operator did not send a price quote for a payment. A decline is one operator’s answer, not the payment’s outcome. See Decline reasons.Decline summary
Thedecline_summary field on payment and quote request status responses: how many settlement operators declined, and why. See Why nobody quoted.
Delivery deadline
The time by which the selected settlement operator must have the payout to the recipient on the destination chain. Sent asfulfillment_deadline. See Deadlines.
Depositor
See Source account.DID (decentralized identifier)
A URI that names a key or a domain, used as the subject or issuer of a verifiable credential. Wallet accounts on Atum usedid:pkh:…; Atum’s issuer uses did:web:…. See What is Atum ID?.
Destination asset
CAIP-19 identifier for the token the recipient receives on the destination rail. See Corridors and assets.E
Environment
Where your payments run: testnet, which moves test tokens, or mainnet, which moves real funds. See Choose an environment.Error code
Thecode on an error response, or on the error of a failed payment, for example NO_QUOTES_RECEIVED. See Error codes.
Escrow
See Settlement vault.EVM
Ethereum Virtual Machine — the execution environment shared by Ethereum, Arbitrum, Base, Celo, and other compatible rails.F
Facilitator
The party in the x402 protocol that verifies a signed payment credential (/verify) and settles it (/settle) on behalf of a resource server. Atum’s facilitator implements the atum-escrow scheme and is keyless — it holds no settlement wallet, so it never takes custody of your funds; instead, settlement operators execute the deposit and delivery transactions. See x402 and the x402 Facilitator API.
Fee
What a payment costs, and who pays it. The payer pays the selected quote’s source amount, which includes the settlement operator’s charge and Atum’s fee. See Fees.Finality
When a transaction can no longer be reversed by its chain. Atum waits for the payout to be final before a payment iscompleted, and a settlement operator may wait for your deposit to be final before it pays a large payment. See Finality.
Fulfillment
The settlement operator delivering tokenized currency to the recipient on the destination chain. See Atum payment lifecycle.FulfillmentProxy
Atum contract on the destination chain that the settlement operator pays the recipient through. It moves the tokens and emits an event Atum reads as evidence of delivery. See Proof of delivery.Fulfillment confirmation
See Settlement receipt.Fulfillment deadline
See Delivery deadline.Fulfillment lock
A lock a settlement operator’s agent holds over a payment while it executes the fulfillment, so a second worker cannot broadcast a competing transaction for the same payment. See Agent error reference.G
Gas
Native rail token (ETH, TRX, CELO, etc.) paid to execute transactions on a rail. Settlement operators hold gas for settlement. Senders need it only for a one-time token approval on EVM chains (Tempo included) and Tron. See Atum infrastructure.H
Holder
The participant who signs a verifiable presentation (the presentation holder) — on Atum, the same account that signed the inner payment request or quote. Not the source account unless those are the same party. See Verifiable presentations.I
Idempotency
Sending the same request again without creating a second payment: the gateway returns what the first request created. See Idempotency.Idempotent retry
Trying the same purchase again (same purchase identifier) so Atum continues that payment instead of starting a new one. See Idempotency.Intent (payment intent)
See Payment request.intentId
In MPP, the per-purchase identifier the acceptance side stamps into the402 challenge. The payer derives the payment’s identity from it. Usually taken from a value the route already carries. See Idempotency.
Issuer (credential)
The party that signed a verifiable credential. Atum issues Known to Atum to participants today. Distinct from a tokenized currency issuer. See Credentials.K
Know Your Agent (KYA)
Who is answerable when software spends on your behalf. See Know Your Agent.Known to Atum
The credential Atum issues to participants today. It means this account is allowed to operate on the network in a named role (payment provider, settlement operator, or Atum-operated service). It is not a compliance statement and not a customer-identity check. See Credentials.M
Max source amount
The most that may leave the source account: the amount delivered plus what the settlement operator charges. It is part of what the payer signs, so it is required on a payment and must equal the signed amount. On a quote request it is optional and only filters quotes. A quote above it is not accepted. See Prepare a payment.MPP (Machine Payments Protocol)
An open, HTTP 402-based protocol for machine-to-machine payments, distinct from x402. MPP has no facilitator role — each payment method (Stripe, Tempo, or Atum’satum-escrow) verifies and settles itself, in-process on the resource server. Atum ships atum-escrow as a native MPP payment method, so your server settles directly against the Payment Gateway, with no separate service in between. See Direct payments (MPP).
Multi-rail
A payment that moves tokenized currency from one payment rail to another (e.g. Arbitrum → Tron). Equivalent to “cross-chain” in blockchain terminology. See Atum infrastructure.N
NO_QUOTES_RECEIVED
The error code on a payment that failed because no usable quote arrived during the quote window. Nobody was selected, so nothing was delivered. See NO_QUOTES_RECEIVED and Why nobody quoted.Nonce reservation
A ledger row a settlement operator’s agent holds while one transaction occupies one nonce on one chain, so two concurrent settlements cannot claim the same slot. See Agent error reference.O
Originator
Organization (PSP, wallet, platform) that submits payment requests to the Payment Gateway. Distinct from the source account that funds the payment — they can be different parties. See Originator vs source account.P
Payment authorization
One-time permission granted by the source account for Atum to move tokens on its behalf. Equivalent to enabling direct debit. Implemented via Permit2. See Token approvals.Payment Gateway
Atum’s REST API to get a price, submit a payment and track its status. Your only integration point. See Network participants.Payment hold
See Settlement vault.payment-identifier
x402 v2 extension that carries a client-supplied purchase identifier inside the payment. The resource server declares it as required in its402; the payer supplies the id in PaymentPayload.extensions. Atum’s facilitator refuses a payment that isn’t anchored to one. See Idempotency and the payment-identifier extension docs.
Payment lifecycle
The stages a payment goes through, from signing to delivery or refund. See Atum payment lifecycle.Payment protocol
A way to pay for an HTTP request with a402 Payment Required exchange: x402 or MPP. See Payment protocols.
Payment rail
An independent network that moves tokenized currency according to its own rules, speeds, and costs. Ethereum, Solana, Tron, Arbitrum, Base, and Celo are each separate payment rails — the same way ACH, SWIFT, and FedWire are separate rails for traditional money. See Atum infrastructure.Payment request
The signed object you create and submit to start a payment. Describes source account, destination account, amount, and authorization. Submitted toPOST /v1/payments. See Payment request.
Payment status
Thestatus of a payment: where it is now and whether that is final. See Payment status.
PaymentSubmitter
In MPP, the server-side seam that settles a verifiedatum-escrow payment. Your server verifies the credential in-process, then hands the payment to a PaymentSubmitter that submits it to the Payment Gateway. It is MPP’s in-process equivalent of the x402 facilitator’s settle step — there is no separate facilitator service. See Accept payments (MPP).
Permit2
Smart contract by Uniswap used on EVM and Tron source rails to implement payment authorization. Requires a one-timeapprove per account and token. See Token approvals.
Phantom broadcast
An RPC node returning success for a transaction it did not actually accept or propagate. Transaction hashes are computed client-side, so a 200 OK is not proof. See Agent error reference.Policy enforcement
Two levers that constrain who may fulfill a payment: an identity list the originator sets on the payment request, and credential-type / issuer trust Atum applies for the environment. See Policy enforcement.Price quote (quote)
A settlement operator’s offer to deliver a payment: the source amount it will take, and its quote expiry. The gateway selects one quote per payment. See Get a price quote.Principal
The person or company that grants an agent authority to act. See Know Your Agent.production-testnet
See Environment.PSP (payment service provider)
Company that offers payment products to merchants or consumers; a common Atum integrator profile.Purchase identifier
The stable identity for one payment. Reused on every attempt at that payment; never across two genuine purchases. In x402 the payer-side carries it (paymentIdentifier / payment-identifier extension); in MPP the acceptance side stamps it as intentId. Derives the gateway’s request_id. See Idempotency.
Q
Quote deadline
See Quote window.Quote expiry
The time a price quote expires, chosen by the settlement operator that made it and sent on the quote asaward_deadline. After it, the quote can no longer be selected. See Deadlines.
Quote selection
How the gateway picks the price quote for a payment: settlement operators send quotes during the quote window, and the gateway selects one that has not expired. See Atum payment lifecycle.Quote window
The time settlement operators have to send price quotes for your payment. It ends atquote_deadline. See Deadlines.
R
Recipient
Address credited on the destination rail. See Network participants.Reconciler
The part of a settlement operator’s agent that watches the chain to resolve a transaction whose outcome is unknown, rather than retrying it blind. See Agent error reference.Reconciliation
Checking each payment against your own records using its ids and its transactions on both chains. See Reconciliation.Refund
Returning the payer’s funds from the settlement vault when the payment is not delivered. See Refunds.Refund reason
Therefund_reason field on a payment that is being refunded: why the settlement operator gave up. See Why it was refunded.
Refund signature
Therefund_signature field on /status when a payment is refund_available. Submit it on the source chain to get your funds back. See Getting your funds back yourself.
request_id
The client-supplied idempotency key the gateway deduplicates on. With the SDK or the API you set it yourself; on x402 and MPP it is derived from the purchase identifier. See Idempotency.Resource server
The server that gates an HTTP route behind payment in the x402 protocol — issues the402 Payment Required challenge and calls the facilitator’s /verify and /settle. Also called the merchant. See Accept payments.
Retry classification
The field on an error saying what to do about it, from a closed set (retry after a delay, fix the request, use a new identifier, and so on). Branch on it, not on the message text. See Error codes.S
Settlement operator
An independent liquidity provider that sends price quotes for payments and delivers the ones it is selected for. You never integrate with settlement operators directly. See Network participants.Settlement provider
See Settlement operator.Settlement receipt
The record of a completed payment: itspayment_id and its transactions on the source and destination chains, in transactions on /status. The transactions are on-chain records that exist independently of Atum, like an ACH trace ID or SWIFT UETR. See What the status response contains.
settlement_pending
x402 settle outcome meaning the payment was accepted and is still settling: re-attempt the same purchase. Distinct fromsettlement_failed (terminal) and from a refusal (nothing charged). See When a payment is still settling.
SettlementPendingError
MPP error raised byverify() when the payment was accepted and is still settling. Carries the gateway paymentId: re-attempt the same purchase. Distinct from SettlementFailedError (terminal) and PaymentRejectedError (nothing charged). See When a payment is still settling.
Settlement vault
The Atum contract on the source chain that holds the payer’s funds while a payment is in progress. Funds leave it only to the selected settlement operator after delivery is verified, or back to the payer. CalledEscrow in contract code. See Settlement vault.
Settler
See Settlement operator. “Settler” appears only in product names: the settler agent and the Settler Gateway.Settler requirements
Optional allow and deny lists of settlement operator identities on a payment request. The originator sets them per payment; Atum applies them. They match named identities, not credential types. See Payment request and Policy enforcement.Source account
The wallet that funds the payment. Distinct from the originator who submits the request. See Network participants.Source asset
CAIP-19 identifier for the token the source account pays from on the source rail. See Corridors and assets.Stablecoin
See Tokenized currency.T
Tempo
Stripe’s L1 blockchain for agentic commerce. Supported by Atum. Notably, Tempo has no native gas token — transaction fees are paid in USD-denominated tokenized currencies (e.g. pathUSD). See Tempo assets for mainnet identifiers and Tempo Moderato assets for the testnet list and the gas note.Timeline
GET /v1/payments/{id}/timeline: the payment’s history, with the transaction hashes on both chains. See Reconciliation.
Tokenized currency
A digital representation of fiat currency that lives on a payment rail. USDC (issued by Circle) and USDT (issued by Tether) are dollar-denominated tokenized currencies. Sometimes called a stablecoin. See Atum infrastructure.Tokenized money
See Tokenized currency.TVM
TRON Virtual Machine — the execution environment for smart contracts on Tron. Atum’s Tron contracts are the TVM counterpart to the EVM settlement contracts. See the EVM and TVM security review (PDF).V
Verifiable credential (VC)
W3C signed JSON document in which an issuer asserts a fact about a subject identifier. On Atum, presented inside a verifiable presentation. See Credentials.Verifiable presentation (VP)
W3C signed wrapper that presents one or more verifiable credentials for a specific payment in a specific environment. The holder signs it. See Verifiable presentations.W
Who owns what
Which party is responsible for each part of a payment: you, Atum, or the settlement operator. See Who owns what.X
x402
HTTP 402-based machine payment protocol. A resource server answers an unpaid request with402 Payment Required; a client signs one of the offered payment options and retries; a facilitator verifies and settles it. Atum offers a native x402 v2 facilitator for the atum-escrow scheme, so the facilitator — not your server — verifies and settles the payment. x402 v2 uses the PAYMENT-SIGNATURE (client → server), PAYMENT-REQUIRED (server → client, on the 402), and PAYMENT-RESPONSE (server → client, on settlement) headers — not the deprecated v1 X-PAYMENT / X-PAYMENT-RESPONSE headers. See Facilitated payments (x402).