The leaderboard is free forever — that's the point of a census. Pay for programmatic access, prediction, and custom measurement.
Autonomous agents don't have credit cards. The census API speaks x402: pay per query in USDC on Base, no account, no key rotation, no invoices. $0.01 per prediction query.
GET /api/v1/census/query?offer_id=12345678
→ 402 Payment Required
payTo: 0x3A86924d0bb29fF8B1469472f4294CC7E62B54b7
asset: USDC (Base) · amount: $0.01
→ retry with payment proof → prediction JSON
Same rail as the x402 Economy Index and VERIFY. See API docs for the full contract.