Here are the requirements for using the Tableau Server REST API:
Tableau Server version: To program with the REST API, you need Tableau Server 9.0 or a later version. Some methods were added in later versions of Tableau Server. The documentation for individual API methods indicates the version of Tableau Server that's required for using that method.
API enabled: By default, Tableau Server is installed with the REST API enabled, but it can be disabled. To disable or enable the REST API, use the tsm configuration set(Link opens in a new window) command. Change the api.server.enabled(Link opens in a new window) setting to true to enable the API or false to disable the API.
Tableau Prep and Tableau Catalog (or Tableau Metadata API): The REST API must be enabled to publish flow output from Prep and to perform a set of tasks using Catalog (or Metadata API).