x402 Facilitator

The DeepNexus Facilitator verifies and settles x402 payments for your API. It checks the payer's EIP-3009 signature, balance and validity window, then submits transferWithAuthorization on-chain and pays the gas — funds go directly from the payer to your payTo address and never pass through DeepNexus.

Get a facilitator key

Open the Facilitator console and log in by signing a message with your wallet (MetaMask, OKX, Rabby, Coinbase Wallet or any EIP-6963 wallet). Signing is free and sends no transaction.
Create a key under API keys. Keys start with fk_ and are shown once.
Every payment verified or settled with your key appears under Settlements.

Base URL

http://localhost:3000/x402

/verify and /settle require Authorization: Bearer fk_.... /supported is public.

GET /supported

Returns the scheme / network pairs this facilitator can settle.

{ "kinds": [ { "x402Version": 1, "scheme": "exact", "network": "base" } ] }

POST /verify

Checks a payment without moving funds.

{
  "x402Version": 1,
  "paymentPayload": {
    "x402Version": 1,
    "scheme": "exact",
    "network": "base",
    "payload": {
      "signature": "0x...",
      "authorization": {
        "from": "0xPayer",
        "to": "0xYourWallet",
        "value": "10000",
        "validAfter": "1767225600",
        "validBefore": "1767225660",
        "nonce": "0x...32 bytes"
      }
    }
  },
  "paymentRequirements": { "scheme": "exact", "network": "base", "maxAmountRequired": "10000", "payTo": "0xYourWallet", "asset": "0x8335...2913", "resource": "https://api.example.com/weather", "description": "", "mimeType": "", "maxTimeoutSeconds": 60, "extra": { "name": "USD Coin", "version": "2" } }
}

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

On failure isValid is false and invalidReason is one of:

Reason	Meaning
`invalid_scheme`, `invalid_network`, `invalid_x402_version`	Payload and requirements don't match, or the network isn't supported
`invalid_exact_evm_payload_signature`	Signature doesn't recover to `from`
`invalid_exact_evm_payload_recipient_mismatch`	`to` is not `payTo`
`invalid_exact_evm_payload_authorization_value`	`value` is less than `maxAmountRequired`
`invalid_exact_evm_payload_authorization_valid_after` / `_valid_before`	Authorization not yet valid or expired
`invalid_transaction_state`	Nonce already used on-chain
`insufficient_funds`	Payer's token balance is too low
`invalid_payload`, `invalid_payment_requirements`	A required field is missing or malformed
`unexpected_verify_error`, `unexpected_settle_error`	The RPC node failed or the transaction could not be sent — safe to retry

POST /settle

Same request body as /verify. Verifies again, then broadcasts the transfer and waits for it to be mined.

{ "success": true, "transaction": "0x...", "network": "base", "payer": "0xPayer" }

On failure: { "success": false, "errorReason": "...", "transaction": "", "network": "base", "payer": "0xPayer" }.

Supported assets

The facilitator settles tokens that implement EIP-3009 transferWithAuthorization, such as USDC on Base, Ethereum, Arbitrum and Polygon. The networks enabled on this server are listed by /supported.

x402 Payment Protocol

8004 Agent Identity