Docs/ERC-1066-x402/Specifications/Schemes

Payment Schemes Specification

v2.0

Payment fulfillment schemes supported by the ERC-1066-x402 gateway.

Overview

Payment schemes define how agents fulfill payment requirements when receiving HTTP 402 responses. ERC-1066-x402 supports multiple schemes with different levels of friction.

The exact Scheme

The exact scheme is the primary payment method for ERC-1066-x402. It requires the payer to fulfill a specific amount to a target address or contract.

Requirements

Precision: The amount must be the exact value requested in the amount field
Atomic Validation: The gateway should verify the payment on-chain before marking the intent as "Allowed"

Execution Flow

1Validation: Agent calls /intents/validate
2Challenge: Gateway returns 402 with the exact scheme requirements
3Payment: Agent or user executes the payment on the specified network
4Finalization: Agent calls /intents/execute
5Success: Gateway verifies the balance/payment and executes the original intent

The onchain Scheme (EVM Extensions)

For EVM-compatible chains, the gateway may also support the onchain scheme, which leverages EIP-712 signatures or ERC-4337 user operations.

EIP-712 Signing

If the network supports it, the extra field will include a domain and types object for the agent to sign a permit or intent:

onchain scheme

{
  "scheme": "onchain",
  "extra": {
    "signatureType": "eip712",
    "domain": { ... },
    "message": { ... }
  }
}

Scheme Selection Logic

If multiple schemes are provided in the accepts array, the agent should prioritize them in the following order:

1
onchain (lowest friction)
2
exact (standard)
3
direct (legacy)

Semantics

Protocols