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Pay for a single NEUS check without creating an account or API key. Three endpoints support this: The exact price for each request is in the PAYMENT-REQUIRED header. It scales with the number of checks, query complexity, and optional add-ons (IPFS pinning, extra chains).

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Flow

1

Request the resource

Send the normal request with the required parameters (address, check IDs, or gate ID).
2

Read the payment requirements

An unpaid request returns HTTP 402. Decode the base64 PAYMENT-REQUIRED response header as an x402 v2 PaymentRequired object.
3

Authorize payment

Use an x402-compatible client to select the supported payment method and sign the payment payload. The private key stays in the client or wallet.
4

Retry the same request

Repeat the identical method, URL, query, and body with the base64 PAYMENT-SIGNATURE request header.
5

Confirm settlement

A successful paid call returns HTTP 200, the result, and a base64 PAYMENT-RESPONSE settlement header.

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Proof check

Check existing receipts before granting access, releasing a payment, or allowing an agent action:
A single-verifier gate check costs 1 credit (0.0025 USDC). The price scales with the number of verifier IDs requested, query complexity, and result limit: The PAYMENT-REQUIRED header always carries the exact amount for that request.

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Proof creation

Create a new trust receipt by paying per call:
Cost = gate check (1 credit) + each verifier’s weight + proof write (2 credits) + optional add-ons. Verifier weights range from 1 (ownership-basic) to 70 (wallet-risk). See Verifiers for per-verifier credit amounts.

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Access grant

Create a signed capability for private-proof sharing:
Base cost: 2 credits. No per-hour surcharge.

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Settlement

Pricing is exact and sub-cent. A 1-credit gate check settles at its unit cost — not a rounded-up minimum. No settlement cap; pay for exactly the credits used. Per-credit price: see Pricing. Always enforce a client-side maximum before signing. Treat the decoded PAYMENT-REQUIRED header as the source of truth for the current amount, asset, recipient, and timeout. After payment, validate all of the following before accepting the result:
  • HTTP status is 200
  • PAYMENT-RESPONSE is present and decodes successfully
  • settlement reports success on the selected network
  • the payer and transaction are present
  • the response body reports a completed operation

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Discovery

The payment challenge includes the x402 v2 Bazaar extension with the HTTP input, JSON output example, and JSON Schema. After the facilitator completes a successful settlement, the resource can be indexed for agent and marketplace search. There is no separate Bazaar registration step. See x402 Bazaar discovery.

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Agent spending limits

Pair x402 with an agent permission receipt to limit autonomous spending.
  • Grant agent-delegation with scope: "payments:x402" and a maxSpend cap.
  • maxSpend is a whole-number string in token base units. For USDC, 25 USDC is "25000000".
  • Use toAgentDelegationMaxSpend('25', 6) from @neus/sdk when constructing the cap.
  • The calling application should also enforce a per-request maximum before signing any payment.
Details: Agent permissions.

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Next

Proof check API

Request and interpret a reusable trust decision.

Billing

Credits, sponsorship, and who pays.

Agent delegation

Scope actions and spending for autonomous agents.
Last modified on July 24, 2026