Paid ($0.01 USDC via x402). One Polymarket feed item: quality-gated mover (vol>=$10k & depth>=$2.5k, +order-book microstructure), whale entry (named whale, with calibration + microstructure), or predetermined signal. Use ?index=N for a specific item, omit for latest. Compute-first / settle-after — you are never charged for an error.