How payment works

The API uses x402 (HTTP 402 Payment Required) with the exact scheme. Settlement is USDC on Base ({network}). There is no account and no API key.

Sequence

1. Call GET or POST on a paid path without a payment header.
2. Read the 402 JSON body (and the PAYMENT-REQUIRED header). accepts[].amount is the price in atomic USDC units (6 decimals).
3. Build a signed x402 payment payload for payTo {payTo}, asset {asset}.
4. Retry the same request with header PAYMENT-SIGNATURE or X-PAYMENT.

Example 402 challenge

{
  "x402Version": 2,
  "error": "Payment required",
  "resource": {
    "url": "https://x402-gateway.forge-x402.workers.dev/api/iban",
    "description": "IBAN validation (ISO 13616 mod-97 checksum + per-country length), returns normalised IBAN, country and BBAN.",
    "mimeType": "application/json"
  },
  "accepts": [
    {
      "scheme": "exact",
      "network": "eip155:8453",
      "amount": "1000",
      "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
      "payTo": "0x7B8bf45ac6AcbA6D4CFB626b57D3f5fF3C9C89F7",
      "maxTimeoutSeconds": 120,
      "extra": {
        "name": "USD Coin",
        "version": "2"
      }
    }
  ]
}

Pay with an x402 client

The easiest path is @x402/fetch (v2) with @x402/evm, which retries the 402 with a signed payment. See Try it in 1 call. Try it in 1 call.

MCP

The same tools are exposed at {mcp} (Streamable HTTP, stateless). Payment is passed in MCP _meta via @x402/mcp. list_endpoints is free. Failed tool calls are not settled.

Loyalty

A credit scheme (every 10 settled calls from one payer address = 1 free call) is planned only: the ledger is not fed from the gateway. See the loyalty note. Read the note.