# Glossary

API terms used across this documentation.

| Term                              | Definition                                                                                                                                                                                        |
| --------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **API key**                       | A bearer credential issued from the dashboard and sent in the `Authorization` header on every request. Starts with `sk_test_...` in test mode.                                                    |
| **ARN**                           | Acquirer Reference Number — a globally unique identifier for a card transaction, returned by some processors.                                                                                     |
| **Authorisation**                 | The issuing bank's reservation of funds against a card. Precedes capture.                                                                                                                         |
| **AVS**                           | Address Verification Service — issuer-side check of the billing address.                                                                                                                          |
| **Bearer token**                  | The authentication scheme SwissPay uses (`Authorization: Bearer sk_test_...`).                                                                                                                    |
| **Capture**                       | The movement of authorised funds into the processor's balance. SwissPay payments auto-capture on authorisation.                                                                                   |
| **CNP**                           | Card Not Present — an e-commerce transaction without a physical card swipe.                                                                                                                       |
| **CVV / CVC**                     | The three- or four-digit security code on a card. Never returned by the API.                                                                                                                      |
| **HTTP 200 with status "failed"** | How SwissPay reports a declined card. The HTTP request succeeded; the issuer declined. Always check `status`, not just HTTP code.                                                                 |
| **Idempotency-Key**               | A header you set on `POST /api/v1/payments` to make retries safe. See [Idempotency](/api-reference/idempotency.md).                                                                               |
| **ISO 4217**                      | The currency code standard (`CHF`, `EUR`, `USD`, etc.).                                                                                                                                           |
| **ISO 3166-1 alpha-2**            | The country code standard (`CH`, `DE`, `US`, etc.).                                                                                                                                               |
| **Issuer**                        | The bank that issued the cardholder's card.                                                                                                                                                       |
| **last4**                         | The last four digits of the card number. The only part of the PAN the API ever returns.                                                                                                           |
| **MCP**                           | [Model Context Protocol](https://modelcontextprotocol.io) — the open protocol that lets AI agents call APIs as tools. See [Using the API with AI agents](/api-reference/using-with-ai-agents.md). |
| **Minor units**                   | Amounts are expressed in the smallest unit of the currency. CHF 29.99 = `2999`.                                                                                                                   |
| **OpenAPI**                       | The machine-readable description of the SwissPay API. See [OpenAPI specification](/api-reference/openapi.md).                                                                                     |
| **PAN**                           | Primary Account Number — the long card number. Never returned by the API.                                                                                                                         |
| **Reference**                     | Your own identifier for a payment, set in the `reference` field. Free text, opaque to SwissPay.                                                                                                   |
| **Scheme**                        | A card network — Visa, Mastercard, AMEX, Diners, Discover, JCB.                                                                                                                                   |
| **Soft descriptor**               | The text that appears on your customer's card statement.                                                                                                                                          |
| **Stored payment method**         | A token that represents a previously seen card, usable on subsequent payments without resubmitting card details.                                                                                  |
| **3-D Secure (3DS)**              | The cardholder-authentication challenge step required by some issuers. Opted into via `authentication: "automatic"`.                                                                              |
| **Webhook**                       | A server-to-server notification — not yet exposed via the public API.                                                                                                                             |
| **Dispute**                       | A chargeback or related challenge raised against a payment. See [Disputes](/api-reference/disputes.md).                                                                                           |
| **Processor**                     | The acquirer/PSP that actually moves funds. See [Payment processors](/reference/integrations.md).                                                                                                 |
| **Rolling reserve**               | A configurable share of settled volume held back for a defined holding period to cover dispute exposure. Configured per merchant.                                                                 |


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