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Quickstart

Choose the path that matches your use case.

Pay for AI with Crypto​

The fastest way to get started is with the x402-openai SDK. It wraps the standard OpenAI client and handles payments transparently.

Python​

pip install x402-openai[evm]
from x402_openai import X402OpenAI
from x402_openai.wallets import EvmWallet

client = X402OpenAI(wallet=EvmWallet(private_key="0x…"))

res = client.chat.completions.create(
    model="openai/gpt-4o-mini",
    messages=[{"role": "user", "content": "Hello!"}],
)
print(res.choices[0].message.content)

TypeScript​

bun add x402-openai @x402/evm viem
import { X402OpenAI } from 'x402-openai';
import { EvmWallet } from 'x402-openai/wallets';

const client = new X402OpenAI({
  wallet: new EvmWallet({ privateKey: '0x…' }),
});

const res = await client.chat.completions.create({
  model: 'openai/gpt-4o-mini',
  messages: [{ role: 'user', content: 'Hello!' }],
});
console.log(res.choices[0]?.message.content);

➡️ Full guide: x402-openai SDK

Gate an HTTP Endpoint with Payments (Rust)​

Use r402 to protect any Axum route with crypto payments:

cargo add r402 r402-evm r402-http
use alloy_primitives::address;
use axum::{Router, routing::get};
use r402_evm::{Eip155Exact, USDC};
use r402_http::server::X402Middleware;

let x402 = X402Middleware::new("https://facilitator.example.com");

let app = Router::new().route(
    "/paid-content",
    get(handler).layer(
        x402.with_price_tag(Eip155Exact::price_tag(
            address!("0xYourPayToAddress"),
            USDC::base().amount(1_000_000u64),
        ))
    ),
);

➡️ Full guide: r402 Server

Build an A2A Agent (Rust)​

Create an agent that speaks the Agent2Agent protocol:

cargo add ra2a
use ra2a::{
    server::A2AServerBuilder,
    types::{AgentCard, AgentSkill},
};

let card = AgentCard::builder("My Agent", "http://localhost:8080")
    .description("A minimal A2A agent")
    .version("1.0.0")
    .skill(AgentSkill::new("chat", "Chat", "General chat", vec![]))
    .build();

A2AServerBuilder::new()
    .executor(MyAgent { card })
    .host("0.0.0.0")
    .port(8080)
    .build()
    .serve()
    .await?;

➡️ Full guide: ra2a Server

Run a Payment Facilitator​

Deploy a facilitator to verify and settle x402 payments:

cargo install facilitator
facilitator init        # generate config.toml
facilitator serve       # start the server

➡️ Full guide: Facilitator

Derive HD Wallets​

Generate multi-chain wallets from a single BIP-39 mnemonic:

cargo install kobe-cli
kobe eth new                    # Ethereum wallet
kobe btc new --address-type taproot   # Bitcoin Taproot
kobe sol new                    # Solana wallet

➡️ Full guide: Kobe CLI