Facilitator API

The OpenX402 facilitator at facilitator.openx402.ai exposes a REST API that x402 middleware calls during the payment flow. These endpoints handle payment verification and on-chain settlement.

`GET /`

Health check endpoint. Returns facilitator status and metadata.

Response

{
  "name": "OpenX402 Facilitator",
  "version": "2.0.0",
  "x402Version": 2,
  "status": "healthy",
  "endpoints": {
    "verify": "/verify",
    "settle": "/settle",
    "supported": "/supported",
    "discovery": "/discovery/resources",
    "list": "/list",
    "whitelist": "/whitelist/:address",
    "register": "https://openx402.ai/register"
  },
  "networks": ["eip155:8453", "eip155:143", "eip155:84532", "solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp"],
  "schemes": ["exact"],
  "features": [
    "EIP-3009 TransferWithAuthorization",
    "Solana SPL Token TransferChecked",
    "CAIP-2 network identifiers",
    "v2 HTTP headers",
    "Discovery extension",
    "v1 backward compatibility"
  ]
}

`GET /supported`

Returns the list of supported payment methods, networks, and the facilitator's signer address.

Response

{
  "kinds": [
    {
      "x402Version": 2,
      "scheme": "exact",
      "network": "eip155:8453",
      "extra": {
        "name": "USD Coin",
        "version": "2",
        "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913"
      }
    },
    {
      "x402Version": 2,
      "scheme": "exact",
      "network": "eip155:143",
      "extra": {
        "name": "USDC",
        "version": "2",
        "asset": "0x754704Bc059F8C67012fEd69BC8A327a5aafb603"
      }
    },
    {
      "x402Version": 2,
      "scheme": "exact",
      "network": "eip155:84532",
      "extra": {
        "name": "USD Coin",
        "version": "2",
        "asset": "0x036CbD53842c5426634e7929541eC2318f3dCF7e"
      }
    },
    {
      "x402Version": 2,
      "scheme": "exact",
      "network": "solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp",
      "extra": {
        "name": "USDC",
        "asset": "EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v",
        "feePayer": "5xvht4fYDs99yprfm4UeuHSLxMBRpotfBtUCQqM3oDNG"
      }
    }
  ],
  "extensions": ["discovery"],
  "signers": {
    "eip155:*": ["0x97316FA4730BC7d3B295234F8e4D04a0a4C093e8"]
  }
}

`POST /verify`

Verifies a signed payment authorization without settling it on-chain. The middleware calls this to validate the payment before serving the protected resource.

Request Body

{
  "paymentPayload": {
    "x402Version": 2,
    "resource": {
      "url": "https://api.example.com/resource",
      "description": "API access",
      "mimeType": "application/json"
    },
    "accepted": {
      "scheme": "exact",
      "network": "eip155:8453",
      "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
      "amount": "100000",
      "payTo": "0xRecipient",
      "maxTimeoutSeconds": 300,
      "extra": {
        "name": "USD Coin",
        "version": "2"
      }
    },
    "payload": {
      "signature": "0x...",
      "authorization": {
        "from": "0xPayer",
        "to": "0xRecipient",
        "value": "100000",
        "validAfter": "0",
        "validBefore": "1700000000",
        "nonce": "0x..."
      }
    }
  },
  "paymentRequirements": {
    "scheme": "exact",
    "network": "eip155:8453",
    "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
    "amount": "100000",
    "payTo": "0xRecipient",
    "maxTimeoutSeconds": 300,
    "extra": {
      "name": "USD Coin",
      "version": "2"
    }
  }
}

Response (Success)

{
  "isValid": true,
  "payer": "0xPayerAddress"
}

Response (Failure)

{
  "isValid": false,
  "invalidReason": "amount_too_low",
  "invalidMessage": "Payment amount is less than required"
}

`POST /settle`

Settles the payment on-chain by executing the transferWithAuthorization call on the USDC contract (EVM) or submitting the TransferChecked transaction (Solana).

Response (Success)

{
  "success": true,
  "transaction": "0xTransactionHash",
  "network": "eip155:8453",
  "payer": "0xPayerAddress"
}

For Solana settlements, transaction is a Solana transaction signature:

{
  "success": true,
  "transaction": "4TH8CXutYEdMnJPTAHQqBRBpVRzJAz7USG24HYP9U43y...",
  "network": "solana",
  "payer": "5xvht4fYDs99yprfm4UeuHSLxMBRpotfBtUCQqM3oDNG"
}

Response (Failure)

{
  "success": false,
  "errorReason": "settlement_failed",
  "errorMessage": "Settlement processing failed",
  "transaction": "",
  "network": "",
  "payer": ""
}

`GET /whitelist/:address`

Check if an address is registered as a whitelisted payment receiver.

Response

{
  "whitelisted": true,
  "address": "0xRecipient"
}

`GET /discovery/resources`

Lists registered resources using the discovery extension. Supports pagination.

Query Parameters

Parameter	Type	Description
`offset`	number	Pagination offset (default: 0)
`limit`	number	Max results per page (default: 100)

Response

{
  "x402Version": 2,
  "items": [
    {
      "x402Version": 2,
      "type": "http",
      "resource": "https://api.example.com/resource",
      "accepts": [
        {
          "scheme": "exact",
          "network": "eip155:8453",
          "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
          "amount": "10000",
          "payTo": "0xRecipient",
          "maxTimeoutSeconds": 60,
          "extra": { "name": "USD Coin", "version": "2" }
        }
      ],
      "metadata": {},
      "lastUpdated": "2026-01-01T00:00:00.000Z"
    }
  ],
  "pagination": {
    "limit": 100,
    "offset": 0,
    "total": 1
  }
}

Error Codes

Error	Description
`unsupported_scheme`	Payment scheme is not `exact`
`unsupported_network`	Network not supported by this facilitator
`amount_too_low`	Payment amount less than required
`recipient_mismatch`	`to` address doesn't match `payTo`
`expired`	Authorization has expired (`validBefore` in the past)
`invalid_signature`	EIP-3009 signature verification failed
`nonce_already_used`	The authorization nonce was already settled
`settlement_failed`	On-chain transaction reverted
`rate_limited`	Too many settle requests (10/min per payer)
`insufficient_balance`	Payer doesn't have enough USDC

Backward Compatibility

The facilitator also supports POST /v1/verify and POST /v1/settle for x402 v1 payloads. V1 requests are automatically converted to v2 format internally.

For Solana networks, both CAIP-2 identifiers (e.g. solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp) and legacy names (solana, solana-devnet) are accepted in verify and settle requests. CAIP-2 identifiers are automatically normalized to legacy format internally before processing.

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