Catalyst adheres to OAuth 2.0 which is an industry-standard protocol for authentication and authorization. The framework enables a host of third-party client applications to gain secure and delegated access to protected resources in Catalyst through APIs. The first step towards obtaining an OAuth authentication token is to register your application with Zoho’s API console and obtain your client_id and client_secret. You must then use them to obtain the Grant token, Access token, and Referesh Token. You can then use the Access Token in the authorization header of your HTTP requests to access Catalyst APIs. Learn about this in detail from the OAuth help documentation.