Sergei Shapoval@TheDuckSaysQuack

The agentic economy is here. AI agents are making decisions, calling APIs, and completing tasks autonomously. But there's a missing layer: how do agents pay for the data they consume? AgentInvoice is that layer. We built payment middleware that wraps any API and adds per-call micropayments via Circle Nanopayments on Arc. When an AI agent calls a paid endpoint, the middleware intercepts the request, processes a USDC nanopayment on Arc, confirms the transaction on-chain, and returns the response - all in under 5 seconds. The problem: Traditional billing (Stripe, subscriptions) is designed for humans. It requires accounts, credit cards, monthly cycles, and $0.30 minimum fees. None of this works for AI agents making 1,000 API calls per hour at $0.001 per call. What we built: - Payment middleware that intercepts API calls and processes Circle Nanopayments - Three demo paid APIs: weather ($0.001), summarize ($0.005), sentiment ($0.002) - Budget enforcement: middleware blocks payments when agent exceeds spending limit - AI agent demo: Grok autonomously decides what data it needs, pays for it, and completes tasks end-to-end The demo shows Grok receiving a task, calling three paid APIs, paying for each autonomously, hitting a budget wall on a complex task, getting blocked by the middleware, and adapting - all without human involvement. Every payment is verified on Arc Block Explorer. Why this matters for Arc: every API call equals one Arc transaction. 1,000 developers × 10,000 calls/day = 10 million transactions/day on Arc. AgentInvoice is the developer onboarding ramp and transaction volume engine for the agentic economy. Tech stack: Node.js, Express, Circle App Kit, @circle-fin/adapter-viem-v2, Viem, Grok API (xAI), Arc Testnet.

In this hybrid hackathon powered by Arc and Circle, developers will build the next generation of Agentic economic applications using Circle’s Nanopayments infrastructure with settlement on Arc in USDC. For the first time, high-frequency, usage-based transactions between users, APIs, and AI agents can operate without gas overhead eroding margin. Arc provides stablecoin-native settlement with predictable, dollar-denominated USDC fees and deterministic, sub-second finality — enabling real-time coordination and economically viable per-action pricing at scale. 📅 April 20 – 26, 2026 • Apr 20 – 25 (Online): Submit projects by Apr 25. • Apr 25 (On-site Build – SF, CA): Teams refine projects. • Apr 26 (On-site Demos & Awards – SF, CA): Live pitches & winners announced. Get guidance from Arc and Circle experts through on-site support. 📍 On-site Venue (April 25-26): MindsDB SF AI Collective 3154 17th St, San Francisco, California, USA 🤝 Go solo or team up, it's your flow. 🏆 Compete for a $15,000+ Prize Pool. 📍 Please note: If approved for the on-site experience, you’ll also have the opportunity to showcase your project live. Travel and accommodation will not be covered. 🧑🏻‍💻 Secure your spot now – sign up before the Kick-Off Stream!