The REST API Definition Metadata in the Talend Studio is the main integration point to leverage artifacts designed in the Talend Cloud API Designer Module within the Talend Studio. Implementations using the API Designer specifications can later benefit from a direct integration with the Talend Cloud API Tester module and by this the new REST API Definition metadata is the entry point to implement a REST Data Service with a contract first approach. It also allows you to import OAS 2.0 Specification from a file in case you get the Specification from elsewhere.
In addition to the REST Data Service use case, it is also supported to import the REST API Metadata in the Talend Data Mapper Module to create structures for mappings of the request and response schemas based on the specification. For more information, see the Talend Data Mapper documentation.