Open APIs V1

Copy page

Get Supported Configurations

This is the V1 API. For new integrations we recommend Get Supported Configurations (V2), which is conformant with the x402 v2 specification.

Code
POST /papi/v1/b402/supported

Returns all payment kinds, extensions, and facilitator signer addresses currently supported by B402.

Request Body

No request body required. Send empty JSON {} or omit the body entirely.

Example

Code
{}

Code
curl -X POST https://{domain}/papi/v1/b402/supported \
-H 'Content-Type: application/json' \
-H 'X-Tesla-ClientId: {your client id}' \
-H 'X-Tesla-SignAccessToken: {your access token}' \
-H 'X-Tesla-Timestamp: {now}' \
-H 'X-Tesla-Signature: {signature}' \
-d '{}'

Response Body

Field	Type	Remarks
kinds	array	List of supported payment kinds
kinds[].x402Version	integer	x402 protocol version (currently 1)
kinds[].scheme	string	Payment scheme (currently "exact")
kinds[].network	string	CAIP-2 network identifier (e.g. "eip155:56")
kinds[].extra	object	Extended details for this kind
kinds[].extra.name	string	Token name (e.g. "U", "USD1", "USDC", "USDT")
kinds[].extra.version	string	Token contract version for EIP-712 signing
kinds[].extra.assetTransferMethod	string	"eip3009", "permit2-exact", or "permit2-upto"
kinds[].extra.facilitatorAddress	string	Facilitator contract address for this transfer method
extensions	array	Supported x402 extensions (currently empty [])
signers	map	Network identifier → list of Facilitator signer addresses

Example

Code
{
  "code": "000000",
  "message": "success",
  "data": {
    "kinds": [
      {
        "x402Version": 1,
        "scheme": "exact",
        "network": "eip155:56",
        "extra": {
          "name": "U",
          "version": "1",
          "assetTransferMethod": "eip3009",
          "facilitatorAddress": "0x1111111111111111111111111111111111111111"
        }
      },
      {
        "x402Version": 1,
        "scheme": "exact",
        "network": "eip155:56",
        "extra": {
          "name": "U",
          "version": "1",
          "assetTransferMethod": "permit2-exact",
          "facilitatorAddress": "0x2222222222222222222222222222222222222222"
        }
      },
      {
        "x402Version": 1,
        "scheme": "exact",
        "network": "eip155:56",
        "extra": {
          "name": "U",
          "version": "1",
          "assetTransferMethod": "permit2-upto",
          "facilitatorAddress": "0x3333333333333333333333333333333333333333"
        }
      },
      {
        "x402Version": 1,
        "scheme": "exact",
        "network": "eip155:56",
        "extra": {
          "name": "USD1",
          "version": "1",
          "assetTransferMethod": "eip3009",
          "facilitatorAddress": "0x1111111111111111111111111111111111111111"
        }
      },
      {
        "x402Version": 1,
        "scheme": "exact",
        "network": "eip155:56",
        "extra": {
          "name": "USD1",
          "version": "1",
          "assetTransferMethod": "permit2-exact",
          "facilitatorAddress": "0x2222222222222222222222222222222222222222"
        }
      },
      {
        "x402Version": 1,
        "scheme": "exact",
        "network": "eip155:56",
        "extra": {
          "name": "USD1",
          "version": "1",
          "assetTransferMethod": "permit2-upto",
          "facilitatorAddress": "0x3333333333333333333333333333333333333333"
        }
      },
      {
        "x402Version": 1,
        "scheme": "exact",
        "network": "eip155:56",
        "extra": {
          "name": "USDT",
          "version": "1",
          "assetTransferMethod": "permit2-exact",
          "facilitatorAddress": "0x2222222222222222222222222222222222222222"
        }
      },
      {
        "x402Version": 1,
        "scheme": "exact",
        "network": "eip155:56",
        "extra": {
          "name": "USDT",
          "version": "1",
          "assetTransferMethod": "permit2-upto",
          "facilitatorAddress": "0x3333333333333333333333333333333333333333"
        }
      },
      {
        "x402Version": 1,
        "scheme": "exact",
        "network": "eip155:56",
        "extra": {
          "name": "USD Coin",
          "version": "2",
          "assetTransferMethod": "permit2-exact",
          "facilitatorAddress": "0x2222222222222222222222222222222222222222"
        }
      },
      {
        "x402Version": 1,
        "scheme": "exact",
        "network": "eip155:56",
        "extra": {
          "name": "USD Coin",
          "version": "2",
          "assetTransferMethod": "permit2-upto",
          "facilitatorAddress": "0x3333333333333333333333333333333333333333"
        }
      }
    ],
    "extensions": [],
    "signers": {
      "eip155:56": ["0x1111111111111111111111111111111111111111"]
    }
  }
}

Notes:

• The response changes infrequently. It is safe to cache the result and refresh periodically (e.g. once per hour).
• facilitatorAddress varies by assetTransferMethod — each transfer method deploys a separate facilitator contract.
• signers lists the authorized settlement addresses. Only transactions signed by these addresses will be accepted on-chain.

Forwarding facilitatorAddress to Buyers (Merchant Responsibility)

⚠️ Required: The merchant MUST forward facilitatorAddress (and the rest of extra) from the /supported response into the paymentRequirements.extra object of the HTTP 402 Payment Required response returned to buyers. Buyers rely on this field to construct a valid Permit2 signature — they cannot, and should not, call /supported themselves (the endpoint is gated by merchant credentials and is not part of the buyer-facing surface).

Per the x402 protocol, buyers never talk to B402 directly; the only channel between buyer and facilitator is the merchant's 402 response. In V1 the facilitatorAddress field is overloaded:

• For assetTransferMethod: "eip3009" it carries the Facilitator EOA (the wallet that submits the on-chain transaction). Buyers do not use it when signing EIP-3009, but it is still useful for traceability.
• For assetTransferMethod: "permit2-exact" and "permit2-upto" it carries the Permit2 proxy contract address — this is the value the buyer must set as permit2Authorization.spender when signing. Without it, the buyer cannot construct a valid signature and B402 will reject with invalid_exact_evm_permit2_payload_spender.
• For assetTransferMethod: "permit2-upto" this same address is what the buyer binds into witness.facilitator — again, buyers have no other way to obtain it.

V2 splits this into two explicit fields (signerAddress / spenderAddress) to remove the overload. See V2 — Get Supported Configurations for the recommended shape.

Field mapping: /supported response → merchant 402 response

From /supported response	Must appear in merchant's 402 response as	Required for
kinds[].extra.facilitatorAddress	paymentRequirements.extra.facilitatorAddress	All methods — especially permit2-exact / permit2-upto, where it is the Permit2 spender.
kinds[].extra.name	paymentRequirements.extra.name	All methods (EIP-712 domain name).
kinds[].extra.version	paymentRequirements.extra.version	All methods (EIP-712 domain version).
kinds[].extra.assetTransferMethod	paymentRequirements.extra.assetTransferMethod	All methods (selects the signing scheme).

Example — merchant 402 response body (permit2-upto)

Code
HTTP/1.1 402 Payment Required
Content-Type: application/json

{
  "x402Version": 1,
  "accepts": [
    {
      "scheme": "exact",
      "network": "eip155:56",
      "amount": "100000000",
      "resource": "https://ai.example.com/api/v1/chat",
      "description": "AI Agent API - per-request billing",
      "payTo": "0x8B3a350e2f3E6B9cC6FB10Fd106bA08f08bec5D2",
      "asset": "0x55d398326f99059ff775485246999027b3197955",
      "maxTimeoutSeconds": 300,
      "extra": {
        "name": "Tether USD",
        "version": "1",
        "assetTransferMethod": "permit2-upto",
        "facilitatorAddress": "0x3333333333333333333333333333333333333333"
      }
    }
  ]
}

Implementation tip: Cache the /supported response on the merchant side and copy facilitatorAddress / name / version / assetTransferMethod from the matching kinds[] entry into every 402 response you emit. Do not hardcode these addresses — they may change when B402 upgrades Permit2 proxies, and /supported is the single source of truth.