Create a stable SHA-256 idempotency fingerprint from a scope and canonical payload without storing state — call when writing a ledger or workflow event that must not double-apply. Use before side effects when composing multi-step agent jobs—the same loyalty/workflow demand band agents already pay for on Bazaar, but fully local. 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.