# API Reference
source: https://developer.mastercard.com/cross-border-services/documentation/api-ref/index.md

Alert: If you are a Customer contracted with MTS EU or MTS UK, you must connect using [OAuth2.0 Authorization Code flow](https://developer.mastercard.com/cross-border-services/documentation/developer-tools/ref-app/oauth2-access-token-based-authentication-details/index.md) for Balance APIs and [OAuth2.0 Request Token based flow](https://developer.mastercard.com/cross-border-services/documentation/developer-tools/ref-app/oauth2-request-token-based-authentication-details/index.md) for all APIs (except Balance API) as the authentication mechanism to ensure compliance with the relevant jurisdiction based Regulatory Technical Standards (either EU or UK) derived from the Revised Payment Services Directive (PSD2). Please proceed to [Getting Started with APIs using OAuth2.0](https://developer.mastercard.com/cross-border-services/documentation/api-basics/index.md#getting-started-with-the-apis-using-oauth-20) for step by step instructions on how to setup. Note: We reserve the right to add parameters to resource actions/services and to add new fields to resource representations returned in responses. These types of changes are considered backward compatible and will added without changing the API version. Applications consuming these resources should be written such that new fields appearing in returned resource representations will not cause errors. We reserve the right to truncate data, when required to comply with constraints of financial messages initiated through calls to the Cross-Border Service API. We will not modify the consumer data in storage, but will perform any required truncation when the financial message is constructed.

## Environment Domains {#environment-domains}

* Sandbox
* Production

```Sandbox
https://sandbox.api.mastercard.com/send
```

```Production
https://api.mastercard.com/send
```

## Swagger UI {#swagger-ui}


API Specification: `https://static.developer.mastercard.com/content/cross-border-services/swagger/cross_border-swagger.yaml`

### Next Steps {#next-steps}

Now that you have a good understanding of all the service's endpoints, proceed to the [Code and Formats](https://developer.mastercard.com/cross-border-services/documentation/code-and-formats/index.md) section to learn about testing the service.