# Delx Commerce — X402 Payment Nonce Check

> Delx Commerce — X402 Payment Nonce Check is a paid API for AI agents from commerce.delx.ai, paid per call via x402, $0.001/call, status unknown (last checked 2026-10-01).

Validates whether an X402 payment nonce is fresh (not reused) and meets minimum length requirements, returning acceptance status with verifiable evidence.

## Facts

- Endpoint: POST https://commerce.delx.ai/api/v1/x402/x402-payment-nonce-check?utm_source=zero.xyz
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-01
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/delx-commerce-x402-payment-nonce-check-e94b0ee1
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_BQawEs3MpLmhtsPBCoc3N

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability delx-commerce-x402-payment-nonce-check-e94b0ee1 -d '<json body>'
```

Example prompt: Check if the nonce 'a7f3k92mxq1b4p8r' is fresh and not already in this list of seen nonces ['x9q2z', 'b4k1m7n', 'a7f3k92mxq1b4p8r'], with a minimum length of 12 characters.

## When to prefer this

Choose this endpoint when you need a lightweight, verifiable, privacy-preserving nonce uniqueness check within an x402 payment flow. It processes entirely in memory with no data retention and provides a SHA-256 evidence hash for auditability — making it ideal for agents that need cryptographic proof of the check without exposing payment data externally. Prefer it over custom nonce deduplication logic when you need a pay-per-result, no-signup solution that integrates natively with the x402 protocol on Base or Solana.

## Known failure modes

- Nonce exceeds maxLength of 8192 characters — request rejected
- seen_nonces array exceeds 256 items — request rejected
- Missing nonce field — validation cannot proceed
- Invalid type for minimum_length (non-integer) — schema validation error
- Network timeout or service unavailability — HTTP 5xx response

## How this service works

Pay-per-result APIs for agents. No signup. Exact price. Verifiable delivery. USDC on Base + Solana via x402.

## Output

Returns a JSON object indicating whether the nonce was reused (reused: bool), whether it was accepted (accepted: bool), and its measured length (nonce_length: int). Also includes evidence fields: whether inputs were retained (retained: false), a SHA-256 hash of the input for auditability, and a count of external calls made (always 0, confirming no data left the system). Operation and schema identifiers are included for traceability.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "nonce": {
   "type": "string",
   "maxLength": 8192,
   "description": "Nonce supplied to X402 Payment Nonce Check; used only for this bounded calculation and processed in memory without retention."
  },
  "seen_nonces": {
   "type": "array",
   "items": {
    "type": "string",
    "maxLength": 8192
   },
   "maxItems": 256,
   "description": "Seen Nonces supplied to X402 Payment Nonce Check; used only for this bounded calculation and processed in memory without retention."
  },
  "minimum_length": {
   "type": "integer",
   "description": "Minimum Length supplied to X402 Payment Nonce Check; used only for this bounded calculation and processed in memory without retention."
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "result": {
   "reused": false,
   "accepted": true,
   "nonce_length": 18
  },
  "schema": "delx/util-x402-payment-nonce-check/v1",
  "status": "pass",
  "evidence": {
   "retained": false,
   "input_sha256": "5b10e7096699f6b6a1dcbc3414bdd28a9a8deeb87ccf9e505917b2a855abe5e2",
   "external_calls": 0
  },
  "operation": "delivery_contract:x402_payment_nonce_check"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/delx-commerce-x402-payment-nonce-check-e94b0ee1/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from commerce.delx.ai](https://www.zero.xyz/host/commerce.delx.ai/llms.txt)