Quickstart

Base URL: https://recallguard-api.vercel.app

1. Read health

curl -s https://recallguard-api.vercel.app/api/v1/health

Health, /, and /openapi.json do not require payment.

2. Call feed or match without a payment

Feed:

curl -s -D - https://recallguard-api.vercel.app/api/v1/feed?limit=1

Match:

curl -s -D - -X POST https://recallguard-api.vercel.app/api/v1/match \
  -H "Content-Type: application/json" \
  -d "{\"items\":[{\"name\":\"Raw Milk Medium Cheddar\",\"brand\":\"Sierra Nevada Graziers\",\"upc\":\"687652165013\"}]}"

Both return HTTP 402. The body is x402Version 1, an error string, and one accepts entry. There is no trial token and no bearer-token bypass on this host.

Feed maxAmountRequired is "50000" ($0.05). Match is "100000" ($0.10). asset is official Base USDC. maxTimeoutSeconds is 60. network is base.

3. Pay

Send the same request with an X-PAYMENT header. The value is base64 JSON:

• x402Version: 1
• scheme: exact
• network: base
• payload.signature: the EIP-3009 signature
• payload.authorization: from, to, value, validAfter, validBefore, nonce

to is the challenge payTo. value is the challenge maxAmountRequired. validAfter can be "0". validBefore has to be inside the 60-second challenge window. A window of about 30 seconds is inside that limit.

The server asks https://facilitator.payai.network to verify the header, runs the handler, then asks the facilitator to settle. The facilitator pays the gas. A handler error is returned without settlement.

4. Read the receipt

A settled response is HTTP 200. The receipt is the X-PAYMENT-RESPONSE header, base64 JSON with success, transaction, network, and payer.

The one confirmed receipt is the match self-test:

{
  "success": true,
  "transaction": "0xf3919e8c55a4e7163cb10e88baa1d4b183d861ff379a54d0d001d932a6325999",
  "network": "base",
  "payer": "0x638FdbB31446B1D4a73a92A2f984C7a1D5FDA339"
}

The on-chain transfer is 100,000 atomic units ($0.10) of Base USDC to 0x90E23A7b6F6494A879d05DDC4278D0e55Dec1e01. Confirm the hash on BaseScan. A 62-character copy of that hash does not resolve.