What command turns on the REST API?

The command that activates the REST API is indeed "rest-api agent." In network devices, REST APIs facilitate communication and management through simple HTTP requests, which are essential for modern network programmability. Enabling the REST API allows various applications and services to interact with the network infrastructure efficiently, promoting automation and integration with tools that manage network resources.

When executed, "rest-api agent" configures the necessary components within the device to listen for and respond to RESTful API calls, thus providing access to configuration data and status information through standardized HTTP methods such as GET, POST, PUT, and DELETE.

The other options may either disable the API or relate to different services not directly involved in activating the REST interfaces. Therefore, this command is crucial for ensuring that the REST API services are operational and capable of handling requests from management software or scripts.