x402

The x402 protocol lets a server request stablecoin payment via the HTTP 402 status code before returning a resource, and it is already live and governed by the x402 Foundation under the Linux Foundation.

In the x402 protocol, when the server receives an unpaid request it returns 402 along with the payment requirements (amount, receiving address, chain, currency); the client constructs an on-chain transfer or signed authorization and replays the request, and the server returns the resource after verification.

x402 is an open protocol that reuses the 402 status code (Payment Required) from the HTTP protocol, enabling software (especially AI Agents) to call APIs on a per-request pay-as-you-go basis and settle directly with cryptocurrency (typically USDC), without requiring accounts, API keys, or traditional checkout pages.

In the x402 purchase intent flow, when the Agent expresses intent it returns a 402 Payment Required challenge containing the price (in smallest units), network, token contract, and seller address; after the facilitator verifies it, the seller receives the signed purchase intent.

A purchase intent is only a signal, not checkout; eBay still completes the actual transaction, and the machine does not ship goods or hold funds in escrow.

x402 is typically combined with stablecoins or on-chain settlement to enable high-frequency micropayments between machines, but its ecosystem maturity, dispute handling and legal compliance frameworks still fall far short of traditional card network networks.

chiefmojo79 uses x402 for per-call endpoints (such as intel/peers and verify-agent) and Stripe for human-purchasable products like the $49 Safety Pack.

Agent-facing per-call invocation should use x402, human-facing finished-product purchases should use Stripe, and when the two coexist, settlement isolation keeps the accounting clear.

Mixing the x402 and Stripe payment channels leads to risks such as confused reconciliation, unclear sources of refund funds, and unclear responsibility for dispute handling.

payTo is the field in API payment protocols (such as x402) used to specify the receiving address; payTo drift means the field is inconsistent with the payment requirements actually returned by the endpoint, which may cause buyers to pay to the wrong address or for the payment to fail.

SML FX Convert requires no SML API key and no account registration; the 402 challenge itself is the complete settlement entry point.

The exact scheme means that an exact amount is required to be paid; eip155:8453 is the CAIP-2 chain identifier of the Base mainnet; USDC is the USD stablecoin on that chain.

The project emphasizes that the latest terms of x402 remain in effect before spending; a 402 challenge is not equal to settlement, and settlement is not equal to acceptance.

The conversion call GET /api/fx/convert?from=USD&to=EUR&amount=100 returns HTTP 402 when unpaid and quotes 1000 atomic units of USDC in the PAYMENT-REQUIRED response header, with the network as eip155:8453 (Base mainnet) and the scheme as exact.

In Own 1's scenario, x402 combined with USDC (a stablecoin pegged 1:1 to the US dollar) enables agents to pay for API calls, compute, or data in a programmable, approval-free manner.

OwnXOS has a built-in crypto wallet that supports x402 USDC payments.

In x402 v2, the PAYMENT-REQUIRED header of the 402 response contains base64-encoded payment terms; in x402 v1, the payment requirements are provided as JSON in the response body for compatibility with older clients.

In the x402 protocol, the facilitator is a separate intermediary service responsible for /verify, which checks the validity of the payment signature (amount, payee, validity period, nonce, etc.), and /settle, which broadcasts the transaction and pays gas to complete the USDC transfer.

x402 recommends the order verify → execute → settle: first validate the signature's validity and balance without broadcasting a transaction, and call settle only after the business logic succeeds, so failed requests incur no charge.

Bazaar is the metadata mechanism in the x402 ecosystem for indexing paid endpoints; the server declares input/output JSON schema, price, and description in the extensions.bazaar field of the 402 response for agent marketplaces or crawlers to discover automatically.