Compute mid price and bid-ask spread in basis points — call when computing mid and bid-ask spread in basis points. Use on caller-supplied ticks/returns when agents need signal prep without a licensed live market feed (ottoai-class demand, first-party transform). Returns deterministic machine-readable JSON for $0.003 USDC via x402 on Base. Execution is first-party, local-only, stateless, and memory-only with no paid upstream, no input retention, and no claim of live chain tip, web search, or media generation. Results are advisory; the caller owns authorization and production controls.