I Built an API Marketplace Where AI Agents Pay Per Request in USDC — 80 Endpoints in 4 Days, Solo

Description and use

AETHERIUS enables AI agents to pay per API request in USDC on Base Mainnet without accounts or keys, leveraging HTTP 402 for crypto payments.

Problem

AI agents need to consume APIs without human sign‑ups, API keys or subscriptions, yet they can transact in crypto.

Outcome

Built solo in 4 days with $5.80 ETH, 80 live endpoints (60 paid, 20 free), 60/60 passing tests, Python & JavaScript SDKs, real USDC payments flowing on Base Mainnet.

Workflow

• 1. Agent sends request to an endpoint. 2. Server responds 402 Payment Required with USDC amount. 3. Agent signs and submits USDC transfer on Base. 4. Server verifies payment via Coinbase CDP. 5. Server returns 200 OK with data.
• 6. Agent can query free x402 Intelligence endpoints for on‑chain analytics without payment.

Evidence

AETHERIUS solves this: An agent hits an API, gets a 402 Payment Required response with a USDC amount, pays on‑chain, and receives data.

Source

80 live endpoints. Python + JavaScript SDKs. All verifiable on‑chain.

Source