- Payments API (
openapi/radiumone-payments-api.yaml) — sessions, purchases, authorizations, captures, voids, refunds, transaction lookups, payment method discovery, and UOB Rewards balance checks. Authenticated with aBeareraccess token exchanged from your API key. Start at the Payments API overview, or jump straight to its reference. - Checkout API (
openapi/radiumone-checkout-api.yaml) — create, retrieve, and cancel hosted-checkout sessions for Hosted checkout. Authenticated by sending your secret key directly as anX-Api-Keyheader — no token exchange. Its reference starts at Create a checkout session.
Hosts
The Payments API is served behind a public gateway path — every request URL
already includes the
/gateway segment shown above (e.g.
https://api-sandbox.radiumone.io/gateway/v1/transactions/purchase). Paths elsewhere in this
reference and in guides are written relative to that base.
See Sandbox and API keys for environment
details and how to get credentials.
Authentication
The two APIs authenticate differently: the Payments API exchanges your key for a short-livedBearer access token, while the Checkout API takes your
secret key directly as an X-Api-Key header on every request. See
Authentication for the full
comparison and both flows —
Payments API
or
Checkout API.
Response envelope
Every Payments API response is wrapped the same way:request_id:
{ "status": "ok", "data": { ... } }. See
Request conventions for the full shape
of both, plus money formats and idempotency.
Errors
Both APIs return errors as RFC 9457application/problem+json bodies — see
Request conventions for the
shared shape and Problem format and retries
for the status guide and retry rules.
Versioning
The Payments API is versioned in the URL path (/v1/...). See
Versioning and deprecation for the compatibility
policy.
Webhooks
Webhook payload shapes (not part of either OpenAPI spec — there’s nowebhooks object) are documented on
Webhook event types.