Source

File: wp-includes/rest-api/endpoints/class-wp-rest-block-renderer-controller.php

public function get_item_schema() {
		if ( $this->schema ) {
			return $this->schema;
		}

		$this->schema = array(
			'$schema'    => 'http://json-schema.org/schema#',
			'title'      => 'rendered-block',
			'type'       => 'object',
			'properties' => array(
				'rendered' => array(
					'description' => __( 'The rendered block.' ),
					'type'        => 'string',
					'required'    => true,
					'context'     => array( 'edit' ),
				),
			),
		);

		return $this->schema;
	}