X402 Networks and Payment Methods

Ace Data Cloud X402 currently settles around USDC and supports two types of chains: EVM and Solana. Different networks have different signing methods, asset addresses, gas behaviors, and applicable scenarios, so you need to choose the network before integration.

Network Identifiers Use CAIP-2

The accepts[].network of x402 v2 is a CAIP-2 identifier, not an abbreviation such as base or skale. Clients must compare by the CAIP-2 string when matching networks:

Network CAIP-2 Identifier
Base eip155:8453
SKALE Base eip155:1187947933
Solana mainnet solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp

Support Matrix

Network scheme Asset Signing Method Applicable Scenario
Base exact Base USDC EIP-3009 TransferWithAuthorization Recommended by default; wallet and liquidity support are mature.
Base upto Base USDC + Permit2 Permit2 PermitWitnessTransferFrom Post-metered APIs such as chat and models.
SKALE exact SKALE bridged USDC EIP-3009 TransferWithAuthorization Low gas cost, suitable for EVM payment verification and low-cost calls.
Solana exact Solana USDC SPL TransferChecked Solana wallets, Agents, or on-chain application scenarios.

upto is currently provided only on Base. The actual available options are subject to the accepts returned by the API. You can also check the Facilitator:

curl https://facilitator.acedata.cloud/supported

The response from Facilitator /supported:

{
  "kinds": [
    { "x402Version": 2, "scheme": "exact", "network": "eip155:8453" },
    {
      "x402Version": 2,
      "scheme": "upto",
      "network": "eip155:8453",
      "extra": { "facilitatorAddress": "0xd019238EAA8a9Ca13C5792Ca10B4029D6ce25708" }
    },
    { "x402Version": 2, "scheme": "exact", "network": "eip155:1187947933" },
    {
      "x402Version": 2,
      "scheme": "exact",
      "network": "solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp",
      "extra": { "feePayer": "3SPm6qbgsDkj24MuR8Ss4sH97fziqyCiqFKDyeVU2igq" }
    }
  ]
}

Explanation of the results:

  • exact on Base, SKALE, and Solana is a fixed-amount payment path.
  • Only Base provides the upto post-metered path, which depends on Permit2 approve.
  • The extra.facilitatorAddress in the upto entry is the address that must be written into the witness when the client signs, and it must be consistent with the value returned by the server.

Base

Base uses the official USDC contract:

0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913

In the exact scheme, the client signs EIP-712 TransferWithAuthorization. The signature content includes:

  • from: payer wallet address
  • to: Ace Data Cloud receiving address
  • value: payment amount for this transaction
  • validAfter / validBefore: signature validity time window
  • nonce: 32-byte random nonce

After verifying the signature, the Facilitator calls USDC's transferWithAuthorization on-chain to complete the transfer.

Base is the most recommended network for production integration, especially suitable for upto post-metering, because the Permit2, USDC, and wallet ecosystems are all more mature.

Example Base exact verification result:

payer 0x5d4f08D5c2bb60703284bc06671Eb680fA41B105
content ADC_BASE_E2E_OK
tx 0x408430ab3451bc22a51e510cdb4b063d6b9686724fea7a31fc109af20f5cd2f3
block 46726299
explorer https://basescan.org/tx/0x408430ab3451bc22a51e510cdb4b063d6b9686724fea7a31fc109af20f5cd2f3
transfer value 95215 atomic USDC

Explanation of the results:

  • The API paid retry returns the model content ADC_BASE_E2E_OK.
  • The on-chain transaction can be queried on BaseScan, and the block number is 46726299.
  • 95215 atomic USDC corresponds to 0.095215 USDC, which is the actual settlement amount for this API call.

Program execution result for order payment using Base exact:

order 78481793-304e-47f7-bc0c-8231aec9cc1e
state Finished
tx 0xfec08cc00a159ea1ec692b32faa9bf3d17595a986301169e689d94f58bc44151
block 46726704
explorer https://basescan.org/tx/0xfec08cc00a159ea1ec692b32faa9bf3d17595a986301169e689d94f58bc44151
transfer value 1200000 atomic USDC

Explanation of the results:

  • The final platform order status is Finished.
  • The order pay_id is written with the same Base transaction hash.
  • 1200000 atomic USDC corresponds to 1.2 USDC, which is the historical actual payment amount for this 10 Credits order under the old policy; new orders no longer receive an additional X402 payment method discount, and the specific signature amount is subject to the 402 response of this transaction.

SKALE

SKALE uses bridged USDC. Its signing method is similar to Base and also uses EIP-3009. It is suitable for EVM payment scenarios with low gas costs; actual calls are still subject to the accepts returned by the API.

A typical SKALE 402 accepts includes:

{
  "network": "eip155:1187947933",
  "scheme": "exact",
  "extra": {
    "name": "Bridged USDC (SKALE Bridge)",
    "version": "2",
    "chainId": 1187947933,
    "verifyingContract": "0x85889c8c714505E0c94b30fcfcF64fE3Ac8FCb20"
  }
}

SKALE currently provides only exact. If you need post-metering, please use Base upto.

Example SKALE exact verification result:

content ADC_SKALE_E2E_OK
tx 0x9fd09901e74c763325fe118b2bc64765c3fca785b86b24a78b97964384db084f
block 1969317
explorer https://skale-base-explorer.skalenodes.com/tx/0x9fd09901e74c763325fe118b2bc64765c3fca785b86b24a78b97964384db084f
paid 0.095215 USDC

Explanation of the results:

  • API paid retry returned model content ADC_SKALE_E2E_OK.
  • The transaction can already be found in the SKALE explorer, and the block number is 1969317.
  • The settlement amount for this exact payment is 0.095215 USDC.

Solana

Solana uses SPL USDC TransferChecked. The client constructs a transfer transaction, signs and submits it, and then puts the transaction signature or serialized transaction into the PAYMENT-SIGNATURE envelope.

Characteristics of Solana:

  • Uses Solana wallet adapter or base58 secret key;
  • The asset is Solana USDC mint;
  • Currently only supports exact;
  • The Facilitator validates the transfer instruction's mint, destination, authority, and amount.

If using wallet fee payer mode, the wallet directly submits the transaction, and the Facilitator is responsible for confirming the transaction and returning the settlement result.

Example of Solana exact validation result:

payer AY2RmGm2zPxB1uKvvF4dKyYdr2VySyL3wcD1MKJZoLRd
HTTP 402 -> HTTP 200
content ADC_SOLANA_E2E_OK
chain signature not confirmed in this run

Result description:

  • The paid retry has already returned HTTP 200, and the model output ADC_SOLANA_E2E_OK.
  • Rate limiting may be encountered when querying the on-chain signature through public RPC.
  • Because public RPC queries may be rate-limited, the Solana explorer is not included here. When strict reconciliation is required, please use your own Solana RPC or platform-side settlement records to confirm the transaction signature.

How to Choose

What you want to do Recommended network
Quickly run through the minimum flow SKALE exact or Base exact
Target ordinary Web3 users Base
Perform post-metering for chat completions and similar use cases Base upto
Solana ecosystem applications Solana exact
Low-cost EVM payment validation SKALE exact

No matter which chain you choose, do not hardcode prices on the client. The price is determined by the accepts[].maxAmountRequired returned by the server.