Submit a spot bid on a biddable domestic shipment routing. Customer, carrier, origin, destination, mode and contract type come from the API key and the routing; the origin factory is left empty when the routing picks up from more than one factory. The DO Email custom column (etv2l0rcfp) is required. Resubmitting the same all-in rate (linehaul + fuel) and expiry on a routing returns your existing bid instead of creating another. Send an Idempotency-Key header to make retries safe: a repeat with the same key returns the bid the first request created (kept 24h), and a repeat while the first is still running returns 409.