x402 Protocol

x402 is an open protocol that lets any HTTP endpoint charge per-request using the 402 Payment Required status code. AXON governs the payment layer between your agent and x402-capable providers.

Payment Flow

When your agent encounters a paywall:

Agent                    Provider                AXON                 Facilitator
  │                         │                      │                       │
  │── GET /resource ───────►│                      │                       │
  │◄── 402 + PAYMENT-REQ ──│                      │                       │
  │                         │                      │                       │
  │── governed_fetch(url, intent) ────────────────►│                       │
  │                         │  Validate Mandate    │                       │
  │                         │  Check Balance       │                       │
  │                         │  Sign Payment        │                       │
  │◄───────────────────── Response ────────────────│                       │
  │                         │                      │                       │
  │── GET + PAYMENT-SIG ───►│                      │                       │
  │                         │── Verify + Settle ──────────────────────────►│
  │                         │◄── Settlement Proof ────────────────────────│
  │◄── 200 + PAYMENT-RESP ─│                      │                       │

x402 Protocol Headers

Header	Direction	Purpose
`PAYMENT-REQUIRED`	Server → Client	Payment terms (amount, asset, recipient, network)
`PAYMENT-SIGNATURE`	Client → Server	Signed EIP-3009 authorization from AXON
`PAYMENT-RESPONSE`	Server → Client	Settlement proof (transaction hash)

Header Compatibility

AXON handles multiple header formats for broad x402 compatibility: Challenge read order:

X-PAYMENT-REQUIREMENTS
PAYMENT-REQUIRED
WWW-Authenticate

Settlement request headers sent:

X-PAYMENT
PAYMENT-SIGNATURE

Receipt read order:

X-PAYMENT-RESPONSE
PAYMENT-RESPONSE

EIP-3009 Settlement

AXON signs payments using EIP-3009 TransferWithAuthorization. This allows gasless USDC transfers where:

AXON signs an authorization off-chain
The x402 facilitator submits the transaction on-chain
USDC transfers from the agent pocket to the provider

What AXON Adds to x402

Capability	x402 alone	With AXON
Payment signing	Agent holds raw key	Agent has mandate-governed pocket
Budget controls	None	Per-transaction, daily, monthly caps
Provider verification	None	Registry matching + attestation
Approval workflows	None	Human-in-the-loop with expiring tokens
Audit trail	Transaction hash only	Full decision + receipt + intent logging
Emergency controls	None	Freeze wallet/department/organization

Getting Started

CLI

Core Concepts

Integrations

Operations

x402 Protocol

Payment Flow

x402 Protocol Headers

Header Compatibility

EIP-3009 Settlement

What AXON Adds to x402

​Payment Flow

​x402 Protocol Headers

​Header Compatibility

​EIP-3009 Settlement

​What AXON Adds to x402

Payment Flow

x402 Protocol Headers

Header Compatibility

EIP-3009 Settlement

What AXON Adds to x402