### Agentic Payments
  - Buy domain (X402): https://api.namefi.io/x402/domain/{domainName}
  - Buy domain (MPP): https://api.namefi.io/mpp/domain/{domainName}?nftReceivingWalletAddress={nftReceivingWalletAddress}

#### x402 Payments (HTTP 402)

Buy a domain with stablecoin (USDC) using the [x402 protocol](https://x402.org). No Namefi account or EIP-712 signing required — the buyer's wallet signs an EIP-3009 `transferWithAuthorization`.

- `GET /x402/domain/{domainName}` — without an `X-PAYMENT` header, returns `402 Payment Required` with payment options (network, asset, amount in USDC). With a valid `X-PAYMENT` header, verifies the signature, starts the registration workflow, and settles payment.
  - Optional query params: `years` (1-10, default 1), `nftReceivingWalletAddress` (defaults to the buyer wallet).
- `GET /x402/purchase/{purchaseId}` — poll purchase status. Returns JSON when `?content-type=json` or the `Accept` header isn't HTML; otherwise redirects to the frontend progress page.
- namefi-skills have the full details about all possible payment options.

#### MPP (Machine Payable Protocol)

Buy a domain or sign in using the MPP payment-challenge flow. The first request returns `402 Payment Required` with a signed challenge; the client signs it (e.g. via the [`mppx`](https://www.npmjs.com/package/mppx) CLI: `mppx sign`) and replays the request with the resulting `Authorization` header to complete the operation.

- `GET /mpp/domain/{domainName}` — register a domain via MPP. Required query param: `nftReceivingWalletAddress` (checksummed). Optional: `years` (1-10, default 1). Without auth → 402 with challenge + price metadata. With a valid signed credential → instant registration.
- `GET /mpp/sign-in` — MPP-authenticated sign-in. Without auth → 402 with challenge. With a valid signed credential → returns the sign-in result.

### Crypto wallet signature (EIP-712)
  **SDK usage:** The SDK handles EIP-712 envelope signing automatically when configured with `type: 'API_KEY'`.

  ### EIP-712 Typed Data Signature (EOA wallets)

  For programmatic use without a stored key, sign each request with your Ethereum wallet.
  See https://docs.namefi.io/docs/02a-eip712-signing for the manual signing flow.

  Required headers:
  - `x-namefi-signer`: Your wallet address (checksummed)
  - `x-namefi-signature`: Hex-encoded EIP-712 signature (`0x`-prefixed)
  - `x-namefi-eip712-type`: The EIP-712 primary type for the operation

  Fetch live EIP-712 metadata from these endpoints (do NOT hardcode types):
  - `GET /v-next/eip712/domain` — signing domain (`{ name: 'Namefi', version: '1' }`, chain-agnostic)
  - `GET /v-next/eip712/types-for-method?method=<operationId>` — accepted primary types and type map for a specific operation
  - `GET /v-next/eip712/types` — full EIP-712 type registry

  Every signed request wraps the payload in an envelope:

      {
        "payloadType": "<PrimaryTypeWithoutEnvelopeSuffix>",
        "payload": { ... },
        "timestamp": <unix-seconds>,
        "nonce": "<unique-random-string>"
      }

  Signatures expire after 300 seconds. Nonces are single-use.

  ### EIP-712 with Smart Contract Wallets (ERC-1271 / EIP-7702)

  If the domain-owning address is a smart contract (e.g. a multisig or smart account), the contract cannot sign directly. Instead:

  1. An approved EOA signer signs the EIP-712 typed data on behalf of the contract.
  2. The contract must implement `approvedSigners(address signer) view returns (bool)` — the API calls this on-chain to verify delegation.
  3. Include one of these headers to indicate the delegating contract address:
     - `x-namefi-eip7702-account`: Preferred header for EIP-7702 delegated accounts
     - `x-namefi-erc1271-account`: Preferred header for ERC-1271 smart contract wallets
     - `x-namefi-eip1271-account`: Legacy alias (same behavior as erc1271)

  When multiple delegation headers are present, precedence is: eip7702 > erc1271 > eip1271.

  The API verifies that `x-namefi-signer` is an approved signer for the contract address across supported chains, then authenticates the request as the contract (domain owner).

  ### SIWE (Sign-In with Ethereum)

  For protected reads that do not require EIP-712. See https://docs.namefi.io/docs/02b-siwe-authentication