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Build AI-powered agents that can autonomously interact with APIs, accept x402 payments, communicate with users, and make decisions. Based on the Coinbase x402 dynamic_agent example, agents can dynamically handle payments and interact with paywalled resources.

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Prerequisites

  • Node.js and npm installed
  • A SKALE Chain endpoint
  • Understanding of x402 protocol
  • Familiarity with TypeScript/JavaScript
  • A facilitator service (see Running a Facilitator)

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Overview

Agents built with x402 can:
  • Make autonomous payments to access paywalled resources
  • Handle dynamic payment requirements
  • Interact with HTTP APIs protected by x402 middleware
  • Process AI responses that require payment

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Quick Start

Install the x402 SDK: 
npm install @coinbase/x402-sdk

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Basic Agent

Here’s a simple agent that can make x402 payments: 
import { X402Client } from '@coinbase/x402-sdk';
import { ethers } from 'ethers';

class SimpleAgent {
  private x402Client: X402Client;
  private wallet: ethers.Wallet;

  constructor(privateKey: string, facilitatorURL: string) {
    const provider = new ethers.JsonRpcProvider('YOUR_SKALE_RPC_URL');
    this.wallet = new ethers.Wallet(privateKey, provider);
    this.x402Client = new X402Client({
      wallet: this.wallet,
      facilitatorURL: facilitatorURL,
    });
  }

  async accessResource(url: string): Promise<any> {
    const response = await fetch(url);
    
    if (response.status === 402) {
      const paymentInfo = await response.json();
      const payment = await this.x402Client.createPayment(paymentInfo);
      await this.x402Client.settle(payment);
      
      const retryResponse = await fetch(url, {
        headers: {
          'X-PAYMENT': JSON.stringify(payment),
        },
      });
      
      return await retryResponse.json();
    }
    
    return await response.json();
  }
}

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Dynamic Agent with AI

An agent that uses AI to decide when to make payments: 
import { X402Client } from '@coinbase/x402-sdk';
import { ChatOpenAI } from '@langchain/openai';
import { AgentExecutor, createReactAgent } from 'langchain/agents';

class AIAgent {
  private x402Client: X402Client;
  private agent: AgentExecutor;

  constructor(privateKey: string, facilitatorURL: string) {
    const provider = new ethers.JsonRpcProvider('YOUR_SKALE_RPC_URL');
    const wallet = new ethers.Wallet(privateKey, provider);
    
    this.x402Client = new X402Client({
      wallet: wallet,
      facilitatorURL: facilitatorURL,
    });

    const paymentTool = {
      name: 'make_payment',
      description: 'Make an x402 payment to access a paywalled resource',
      execute: async (url: string) => {
        return await this.accessPaywalledResource(url);
      },
    };

    const llm = new ChatOpenAI({ modelName: 'gpt-4' });
    this.agent = createReactAgent({
      llm,
      tools: [paymentTool],
    });
  }

  async accessPaywalledResource(url: string): Promise<any> {
    const response = await fetch(url);
    
    if (response.status === 402) {
      const paymentInfo = await response.json();
      const payment = await this.x402Client.createPayment(paymentInfo);
      await this.x402Client.settle(payment);
      
      const retryResponse = await fetch(url, {
        headers: {
          'X-PAYMENT': JSON.stringify(payment),
        },
      });
      
      return await retryResponse.json();
    }
    
    return await response.json();
  }

  async processRequest(userRequest: string): Promise<string> {
    const result = await this.agent.invoke({
      input: userRequest,
    });
    
    return result.output;
  }
}

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Agent with LangChain Integration

Integrate x402 payments with LangChain agents: 
import { createX402PaymentTool } from '@openlibx402/langchain';
import { ChatOpenAI } from '@langchain/openai';
import { AgentExecutor, createReactAgent } from 'langchain/agents';

const paymentTool = createX402PaymentTool({
  walletKeypair: yourKeypair,
  maxPayment: '5.0',
  facilitatorURL: 'https://facilitator.dirtroad.dev',
});

const agent = createReactAgent({
  llm: new ChatOpenAI(),
  tools: [paymentTool, ...otherTools],
});

const result = await agent.invoke({
  input: 'Get data from http://localhost:3000/premium-data',
});

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Resources