Quote before every order. The response prices the order and tells you which providers can serve it — and for headless, which of them can serve it headlessly, which is a smaller set.
The endpoint, its parameters and the full response are in the API reference. Two things differ on the headless path.
1. Ask for headless quotes
Endpoint: POST /payments/crypto/quote?integrationMode=HEADLESS
integrationMode decides which providers are queried and whether the headless-support filter is applied. It takes WIDGET (the default), HEADLESS, or ALL.
At 2026-05-01 each quote also carries fields the order needs:
Pass customerId whenever you have one, so ramp intelligence and previously-used scoring apply.
Header: Meld-Version: 2026-05-01
integrationMode arrived in 2026-05-01. An older version silently ignores it — no error, no warning, just widget quotes. You then create a headless order against a provider that never offered one, and the failure surfaces at order creation instead.
Next
Check eligibility for the provider you chose, then create the order.