> For the complete documentation index, see [llms.txt](https://xdocs.ngd.network/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://xdocs.ngd.network/integrations/x402.md).

# 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](/integrations/x402/contracts.md)

## Facilitators

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

[Ax402](https://ax402.io/) 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](https://github.com/x402-foundation/x402/tree/main/typescript)
* Python: [x402/python](https://github.com/x402-foundation/x402/tree/main/python)
* Go: [x402/go](https://github.com/x402-foundation/x402/tree/main/go)

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

* SDK: [`@ax402/sdk`](https://www.npmjs.com/package/@ax402/sdk) (includes buyer-side helpers)
* CLI: [`@ax402/cli`](https://www.npmjs.com/package/@ax402/cli)
* MCP server: [`@ax402/mcp-server`](https://www.npmjs.com/package/@ax402/mcp-server)
* React paywall: [`@ax402/react-paywall`](https://www.npmjs.com/package/@ax402/react-paywall)

Source and additional language SDKs (Python, Go) are in the [ax402-sdks](https://github.com/axLabs/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](/integrations/x402/quick-start.md)

## Network Addresses

Deployed contract addresses are listed in: [Networks](/development/networks.md)

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