AI agents (x402)
Let AI agents pay per request in USDT with the standard x402 protocol and Tazor as the facilitator.
x402 lets an AI agent pay for an API call in the same HTTP request. Tazor runs a facilitator for Whitechain: your API asks for a price, the agent signs one USDT transfer for that price, and the facilitator checks it and settles it on Whitechain. The agent needs USDT but no WBT for gas.
How a paid request works
- The agent calls your API without paying. Your API answers 402 Payment Required with the payment requirements below.
- The agent signs a USDT
transferWithAuthorizationto your address for at most that amount, valid for up to an hour. - It repeats the call with the signed payment in the
X-PAYMENTheader. - Your API asks the facilitator to verify the payment, serves the response, then asks it to settle. The USDT arrives in about a second.
Payment requirements
{
"scheme": "exact",
"network": "whitechain-sepolia",
"maxAmountRequired": "10000", // 0.01 USDT (6 decimals)
"asset": "0xcedfB56113143d55b2358b8CFbB0dEB5Ad2f55a7",
"payTo": "0x…your address",
"resource": "https://api.example.com/report",
"extra": { "name": "Tether USD", "version": "1" }
}The network id eip155:1874 is accepted too.
Facilitator endpoints
| Method | Path | What it does |
|---|---|---|
| GET | /x402/supported | Lists the schemes and networks it settles. |
| POST | /x402/verify | Checks the signature, the amount, the balance and that the authorisation is unused. |
| POST | /x402/settle | Simulates, then submits the transfer and returns the transaction. |
Bodies follow the x402 specification: { x402Version, paymentPayload, paymentRequirements }.
Limits that protect the facilitator
- An authorisation may be valid for at most one hour, and for no more than the price you asked.
- Every settlement is simulated before it is sent; per-agent and per-day limits apply.
Payments to you appear in Checkout, Agents, with the agent's address, the resource and the transaction.
This build runs on Whitechain Sepolia with test USDT.