x402 (Agent-Driven Payments)

Overview

x402 enables agent-driven, authorization-based payments on Neo X.

Instead of requiring users to submit and fund transactions directly, x402 allows agents to:

• obtain payment requirements from a service

• collect payment authorizations from users

• submit settlement transactions on-chain

This enables machine-native payment flows where authorization and execution are separated.

Why x402 on Neo X

Neo X is well-suited for agent-driven payment flows:

• fast finality enables predictable settlement

• EVM compatibility allows reuse of established standards such as Permit2

• native asset support enables efficient value transfer

• low-latency execution fits automated agent systems well

x402 builds on these properties to support:

• off-chain authorization and on-chain settlement

• gas abstraction, where agents submit transactions and pay gas

• programmable payment flows with explicit settlement constraints

Contracts

The x402 integration relies on the following contracts:

• Permit2 A signature-based token authorization primitive used for delegated transfers.

• x402ExactPermit2Proxy An x402 settlement contract that acts as the authorized spender in Permit2 signatures and enforces x402-specific payment constraints.

See: Contracts

Facilitators

Settlement can be submitted by any agent, relayer, or facilitator that can call the on-chain settlement contract.

Ax402 provides a facilitator for Neo X. Creating an account gives you an API key with free settlements.

SDKs and tooling

To implement buyers, sellers, or settlement helpers, start from the open-source x402 client libraries:

• TypeScript: x402/typescript

• Python: x402/python

• Go: x402/go

If you use the Ax402 facilitator, additional packages are available for platform management, buyer helpers, agent tooling, and React paywalls:

• SDK: @ax402/sdk (includes buyer-side helpers)

• CLI: @ax402/cli

• MCP server: @ax402/mcp-server

• React paywall: @ax402/react-paywall

Source and additional language SDKs (Python, Go) are in the ax402-sdks repository.

Quick Start

A typical x402 flow looks like this:

1. A service defines payment requirements

2. The user signs an authorization

3. An agent submits settlement on-chain

4. The payment is executed through the x402 contract using Permit2

See: Quick Start

Network Addresses

Deployed contract addresses are listed in: Networks

This page focuses on integration and usage rather than deployment details.