What essential action is required when using the Document API?

The essential action required when using the Document API is to update connection information in workbooks and data sources. The Document API provides capabilities for programmatically interacting with Tableau workbooks, allowing users to modify elements like connections to data sources. If the data source details, such as server name or database credentials, change, the Document API can be used to quickly update this information across multiple workbooks. This functionality is crucial in environments where data connections are frequently adjusted, ensuring that reports and dashboards remain functional without needing to manually update each one.

The other options relate to different functionalities within Tableau, but they do not accurately reflect the primary purpose of the Document API. Deleting outdated data sources typically involves managing the content directly within Tableau Server or Desktop rather than through the Document API. Exporting visualizations is usually handled through different export functionalities in Tableau rather than through the Document API. Installing custom extensions pertains to the integration of additional functionality into Tableau, a process separate from the capabilities provided by the Document API.