How I Built an Autonomous AI Agent That Earns USDC While I Sleep

Description and use

An autonomous agent that automatically accepts USDC via x402, signs transactions, and retries requests after payment, enabling passive income.

Problem

Create a minimal, production‑ish AI‑driven service that autonomously charges USDC via the x402 protocol without manual intervention.

Outcome

The agent autonomously charges USDC, signs transfers, and retries requests, generating passive income while remaining stateless and compatible with any HTTP client.

Workflow

• 1. Set up FastAPI app exposing desired endpoints.
• 2. Implement x402 middleware to return 402 with payment details when no payment header is present.
• 3. Create a Wallet Manager singleton that loads an Ethereum private key and signs USDC transfer transactions via web3.py.
• 4. Configure the USDC contract address and ABI for Base network.
• 5. On receiving a 402 response, the client automatically fetches USDC, signs the transaction, and retries the request.
• 6. Deploy the service and fund the wallet with USDC.
• 7. Monitor transactions and revenue via logs or dashboards.

Evidence

x402 is a lightweight HTTP‑based payment scheme that lets a server respond with a 402 Payment Required status and a payment request in the WWW‑Authenticate header.

Source

Agent Service – a FastAPI app that exposes one or more useful endpoints (e.g., text summarization, image tagging). Each endpoint checks for a valid x402 payment; if missing, it returns a 402 with payment details.

Source