The Developer Portal on the Tableau Community is the place to go for everything related to extending and automating Tableau. There you can get access to the following:
REST API—Manage provisioning, permissions, and publishing on Tableau Server or Tableau Online via HTTP. The REST API gives you access to the functionality behind the data sources, projects, workbooks, site users, and sites. You can use this access to create custom applications or to script interactions with server resources.
Tableau SDK—Use C, C++, Java, or Python to create extracts from any data and then to publish your extracts.
ODBC connector—Create a connection using ODBC (Open Database Connectivity), which is a data-access protocol that’s supported by a wide array of data sources. In Tableau Desktop, you can connect to any ODBC-compliant source using the built-in ODBC connector.