How x402 Gasless Payments Actually Work

Every time an AI agent calls a paid MCP endpoint on OMA-AI, a payment is settled in USDC — without the agent paying gas. Here's how.

The Problem with Normal Crypto Payments

In a typical Ethereum transaction:

User signs a transaction
Pays gas (gas price × gas used)
Waits for block confirmation
Payment settles

For a $0.001 AI agent API call, paying $0.02 in gas makes no sense.

Enter EIP-3009: TransferWithAuthorization

x402 uses EIP-3009, which allows gasless USDC transfers:

TransferWithAuthorization {
  from: agent_wallet,
  to: publisher_wallet,
  value: 1000,  // 0.001 USDC in micro-units
  validAfter: 0,
  validBefore: timestamp + 1 hour,
  nonce: unique_per_transaction,
  v, r, s: EIP-712 signature from agent_wallet
}

The key innovation: the publisher (relayer) submits the transaction and pays gas, but the agent pays for it indirectly through a fee built into the payment.

The Relayer Model

Agent → Signs EIP-3009 off-chain → Publisher → Submits to chain → Gets gas reimbursed
         + payment in USDC                              + small fee

The relayer (OMA-AI) front-runs gas and earns a 0.5-1% fee. The agent never touches gas. Publishers get USDC directly.

EIP-712 Signatures

The agent signs a structured EIP-712 message:

OMA-AI Payment Request
Domain: oma-ai.com
Version: 1
Chain: 8453 (Base mainnet)
Nonce: 0x...
Max Amount: 1000000  // $1 max
Payer: 0xAgentWallet

This is the same standard used by Circle's USDC and many institutional custody solutions.

On Base vs Ethereum Mainnet

Base: ~$0.001 gas per transaction. Cheap enough that even tiny payments work.
Ethereum mainnet: ~$3-10 gas. Only viable for larger payments.
Solana: SPL-USDC transfers are $0.00025 each. Truly feeless.

OMA-AI supports both chains, automatically selecting the cheapest route.

Verification

When a publisher receives a payment request, they verify:

Signature matches the claimed agent wallet
Nonce hasn't been used (prevents replay attacks)
Amount is within agreed limits
Timestamp hasn't expired

Only then does the relayer submit the on-chain transaction.

How x402 Gasless Payments Actually Work