Reference implementations: Crossmint Agentic Finance

Reference implementations showing AI agents making autonomous blockchain payments using Crossmint wallets.

Prerequisites

Required:

• Node.js 18.17.0+
• npm 9.0.0+
• Crossmint API key - Get one

For blockchain interactions:

• Testnet USDC - Circle faucet
• Basic understanding of smart contracts and wallets

Glossary:

• x402: HTTP payment protocol using 402 Payment Required status code
• A2A: Agent-to-Agent - protocol for AI agents to communicate and transact
• EOA: Externally Owned Account - traditional wallet controlled by private key
• MCP: Model Context Protocol - standard for AI tool integration

Quick Start

Simplest demo:

# Clone repository
git clone https://github.com/crossmint/crossmint-agentic-finance.git
cd crossmint-agentic-finance

# Run basic x402 paywall
cd ping
cp .env.example .env
# Edit .env: Set PAY_TO to your address
npm install
npm run dev

# Test in another terminal
curl -i -H "Accept: application/json" http://localhost:3000/ping
# Returns 402 Payment Required with payment details

Learn the payment flow: See ping/README.md for generating payment headers and testing settlements.

Demos by Use Case

HTTP Paywalls (Start Here)

Minimal servers requiring USDC payment to access endpoints.

Start with: ping for pure backend, ping-crossmint for full-stack

Agent-to-Agent Payments

Autonomous agents paying each other for services and tool access.

Start with: hello-eoa-a2a for basics, events-concierge for production patterns

Production/Real World Examples

Real-world implementations with advanced features.