> ## Documentation Index
> Fetch the complete documentation index at: https://docs.xentfi.com/llms.txt
> Use this file to discover all available pages before exploring further.

# x402 SDK API Reference

> Full reference for X402FacilitatorClient, its methods, and the x402 type surface.

## `new X402FacilitatorClient(options)`

| Option   | Required | Description                       |
| -------- | -------- | --------------------------------- |
| `apiKey` | ✅        | Your XentFi WAAS API key.         |
| `orgId`  | ✅        | Your XentFi WAAS organization ID. |

<Note>
  The facilitator URL (`https://api.xentfi.com/v1/x402`) and relayer wallet are fixed on the backend — they are not configurable in the client. Every request sends `apiKey`/`orgId` as the `apikey`/`orgid` headers.
</Note>

## Methods

### `getSupported()`

```ts theme={null}
getSupported(): Promise<SupportedResponse>
```

Lists all (chain, asset) pairs and schemes this facilitator supports. **No authentication required** — safe to call before you have `apiKey`/`orgId` configured, e.g. to build a merchant's `accepts` list dynamically.

### `verify(paymentPayload, paymentRequirements)`

```ts theme={null}
verify(
  paymentPayload: PaymentPayload,
  paymentRequirements: PaymentRequirement
): Promise<VerifyResult>
```

Verifies a payment payload against a requirement — checks the EIP-712 signature, amount, recipient, and validity window. Returns `{ isValid: true }` on success; **throws** on failure (see [Error Handling](/x402/errors)).

### `settle(paymentPayload, paymentRequirements)`

```ts theme={null}
settle(
  paymentPayload: PaymentPayload,
  paymentRequirements: PaymentRequirement
): Promise<SettleResult>
```

Settles a payment by submitting the `TransferWithAuthorization` on-chain via your organization's WAAS relayer wallet, which pays gas. Returns `{ success: true, txHash, network }` on success; **throws** on failure.

## Types

### `PaymentRequirement`

What a resource server demands to be paid, expressed to the client in the `402` challenge.

```ts theme={null}
interface PaymentRequirement {
  scheme: "eip3009";
  network: string;
  blockchainId: string;
  assetId: string;
  maxAmountRequired: string; // decimal string, in the token's own units
  payTo: Address;
  resource: string;
  description?: string;
  maxTimeoutSeconds: number;
}
```

### `X402Challenge`

The full `402` response body.

```ts theme={null}
interface X402Challenge {
  x402Version: 1;
  accepts: PaymentRequirement[];
}
```

### `PaymentPayload` / `Eip3009SchemePayload`

What the payer sends back (base64-encoded) as the `X-PAYMENT` header. Currently the only supported scheme is `eip3009`; `PaymentPayload` is an alias for `Eip3009SchemePayload`.

```ts theme={null}
interface Eip3009SchemePayload {
  scheme: "eip3009";
  from: Address;
  to: Address;
  value: string;        // token base units, decimal string
  validAfter: string;   // unix seconds
  validBefore: string;  // unix seconds
  nonce: Hex;
  signature: Hex;
}
```

### `VerifyResult` / `SettleResult`

```ts theme={null}
type VerifyResult = { isValid: true };
type SettleResult = { success: true; txHash: Hex; network: string };
```

Both are the *success* shape only — failures throw instead of returning a falsy result (see [Error Handling](/x402/errors)).

### `SupportedResponse`

```ts theme={null}
interface SupportedResponse {
  protocolVersion: string;
  facilitatorAddress: string;
  supportedConfigurations: SupportedConfiguration[];
}

interface SupportedConfiguration {
  network: { id: string; name: string; type: string };
  gasSponsorship: { enabled: boolean; maxSponsorshipValueUsd?: string };
  tokens: Array<{
    id: string;
    name: string;
    symbol: string;
    address: string;
    decimals: number;
    version: string;
    supportedSchemes: Array<{
      type: string;
      methods: string[];
      contractAddress?: string;
    }>;
  }>;
}
```

### `Eip3009TokenDomain`

Needed if you use the signing helpers — see [EIP-3009 Signing Reference](/x402/signing) for full detail.

```ts theme={null}
interface Eip3009TokenDomain {
  chainId: number;
  tokenAddress: Address;
  tokenName: string;
  tokenVersion: string;
  tokenDecimals: number;
}
```

## All exports

```ts theme={null}
import {
  X402FacilitatorClient,
  X402FacilitatorError,
  X402FacilitatorNetworkError,
  X402FacilitatorConfigError,
  signEip3009Authorization,
  buildEip3009Domain,
  TRANSFER_WITH_AUTHORIZATION_TYPES,
} from "@xentfi/x402-facilitator";

import type {
  X402FacilitatorClientOptions,
  SignExactAuthorizationParams,
  RetryOptions,
  X402Scheme,
  PaymentRequirement,
  X402Challenge,
  Eip3009SchemePayload,
  PaymentPayload,
  VerifyResult,
  SettleResult,
  SupportedResponse,
  SupportedConfiguration,
  Eip3009TokenDomain,
} from "@xentfi/x402-facilitator";
```

## Next steps

<CardGroup cols={2}>
  <Card title="Resource Server Guide" icon="server" href="/x402/resource-server">
    See `verify`/`settle` used end-to-end.
  </Card>

  <Card title="Error Handling" icon="alert-triangle" href="/x402/errors">
    Error classes and HTTP status mapping.
  </Card>
</CardGroup>