Source

File: wp-includes/rest-api/class-wp-rest-server.php

public function __construct() {
		$this->endpoints = array(
			// Meta endpoints.
			'/' => array(
				'callback' => array( $this, 'get_index' ),
				'methods'  => 'GET',
				'args'     => array(
					'context' => array(
						'default' => 'view',
					),
				),
			),
		);
	}