Register an order for shipping-insurance coverage, spending the offer_id returned by a quote. The offer token is single-use, and Mulberry derives the insured value from the order breakdown rather than accepting it from the caller. Re-registering the same external_order_id returns the existing policy instead of creating another.

The token is checked before the payload, so a missing, unrecognized or malformed Authorization header returns 401 whatever the body.

Mulberry derives the coverage amount rather than accepting it: min(order_items_subtotal - premium, quoted_value) + min(order_shipping + order_tax, quoted_value). Each half is capped at the quoted value independently, so coverage can exceed what you quoted — the ceiling is twice quoted_value. An order_items_subtotal that omits the premium under-insures the order rather than failing, and one at or below the premium is rejected.

Retailer-paid orders. With retailer_paid: true there is no quote: the insured value is the item subtotal plus shipping and tax (shipping and tax capped at the item subtotal), the customer premium is recorded as $0, and no order email is sent to the shopper. offer_id and premium must be omitted and customer must carry an email. Errors: 400 Retailer-paid registration is not enabled for this retailer, 400 Field required when retailer_paid (customer), 400 must be omitted when retailer_paid (offer_id, premium), and 409 Order already registered with a different payer when an external_order_id was first registered the other way.