coinmarketcap-official/skills-for-ai-agents-by-coinmarketcap/cmc-x402

CoinMarketCap x402

Pay-per-request crypto market data powered by the x402 protocol. Access CoinMarketCap endpoints instantly with on-chain USDC payment. No API key or subscription required.

What is x402?

x402 is an open payment protocol developed by Coinbase that enables automatic stablecoin payments over HTTP. Instead of managing API keys, you pay $0.01 USDC per request on Base. The x402 client library handles payment signing automatically.

Learn more: https://docs.x402.org

Prerequisites

Before using x402 endpoints, ensure you have:

1. Node.js 18+ and npm installed
2. Base network wallet with a private key you control
3. USDC on Base to pay for requests ($0.01 per request)
4. Small amount of ETH on Base for gas fees

Use Cases

Get current prices for specific coins: Use /x402/v3/cryptocurrency/quotes/latest with symbol or id parameter. Example: Get BTC and ETH prices for a portfolio tracker.

List top cryptocurrencies: Use /x402/v3/cryptocurrency/listing/latest with limit parameter. Example: Display top 100 coins ranked by market cap.

Search for DEX tokens: Use /x402/v1/dex/search with keyword parameter. Example: Find a memecoin by name when you don't know the contract address.

Get DEX pair trading data: Use /x402/v4/dex/pairs/quotes/latest with pair address. Example: Monitor liquidity and volume for a specific Uniswap pool.

AI agent data access: Use the MCP endpoint at https://mcp.coinmarketcap.com/x402/mcp. Example: Let Claude or other LLMs fetch live crypto data with automatic payment.

Quick Start

Install the x402 TypeScript SDK:

npm install @x402/axios @x402/evm viem

Fetch data with automatic payment:

import { createX402AxiosClient } from "@x402/axios";
import { ExactEvmScheme, toClientEvmSigner } from "@x402/evm";
import { privateKeyToAccount } from "viem/accounts";
import { createPublicClient, http } from "viem";
import { base } from "viem/chains";
// SECURITY: Never hardcode private keys in source code.
// Use environment variables: process.env.PRIVATE_KEY
// For production, use a dedicated hot wallet with limited funds.
const account = privateKeyToAccount(process.env.PRIVATE_KEY as `0x${string}`);
const publicClient = createPublicClient({ chain: base, transport: http() });
const signer = toClientEvmSigner(account, publicClient);
const client = createX402AxiosClient({
  schemes: [new ExactEvmScheme(signer)],
});
const response = await client.get(
  "https://pro.coinmarketcap.com/x402/v3/cryptocurrency/quotes/latest",
  { params: { symbol: "BTC,ETH" } }
);
console.log(response.data);

Endpoints

Base URL: https://pro.coinmarketcap.com

All parameters from the standard CMC Pro API work with x402 endpoints. See endpoints.md for full parameter reference.

MCP for AI Agents

The x402 MCP endpoint lets AI agents access CMC data with automatic payment.

Connection URL:

https://mcp.coinmarketcap.com/x402/mcp

Transport: Streamable HTTP (POST)

Connect using any MCP client with an x402-aware HTTP transport. The server exposes the same tools as the REST endpoints and supports automatic tool discovery.

Pricing

$0.01 USDC per request on Base (Chain ID: 8453).

Payment only occurs on successful data delivery. If the request fails, no payment is deducted.

References

• endpoints.md - Full parameter reference for all endpoints
• payment-details.md - 402 response format, contract addresses, manual integration

Resources

• x402 Protocol: https://x402.org
• x402 Documentation: https://docs.x402.org
• x402 GitHub: https://github.com/coinbase/x402
• CMC API Documentation: https://coinmarketcap.com/api/documentation