REST API is the correct option for invoking an endpoint by default after deploying a model for online inference.

The cloud prediction endpoints are exposed as RESTful services and the primary programmatic interface is the REST API. You call the endpoint with standard HTTP requests to the predict method to obtain online predictions and this is the default protocol used for automated or production traffic.

Python client library is not the default method even though it provides a convenient SDK. The client library is a higher level wrapper that itself calls the underlying REST API.

Cloud Console UI is not the default method for programmatic invocation because the console is intended for manual testing and exploration rather than automated requests.

gcloud CLI is not the default method either because it is a command line tool that wraps the same REST API and is used for scripting and management rather than being the native protocol.

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