WP_REST_Search_Controller::get_item_schema

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

		$types    = array();
		$subtypes = array();

		foreach ( $this->search_handlers as $search_handler ) {
			$types[]  = $search_handler->get_type();
			$subtypes = array_merge( $subtypes, $search_handler->get_subtypes() );
		}

		$types    = array_unique( $types );
		$subtypes = array_unique( $subtypes );

		$schema = array(
			'$schema'    => 'http://json-schema.org/draft-04/schema#',
			'title'      => 'search-result',
			'type'       => 'object',
			'properties' => array(
				self::PROP_ID      => array(
					'description' => __( 'Unique identifier for the object.' ),
					'type'        => 'integer',
					'context'     => array( 'view', 'embed' ),
					'readonly'    => true,
				),
				self::PROP_TITLE   => array(
					'description' => __( 'The title for the object.' ),
					'type'        => 'string',
					'context'     => array( 'view', 'embed' ),
					'readonly'    => true,
				),
				self::PROP_URL     => array(
					'description' => __( 'URL to the object.' ),
					'type'        => 'string',
					'format'      => 'uri',
					'context'     => array( 'view', 'embed' ),
					'readonly'    => true,
				),
				self::PROP_TYPE    => array(
					'description' => __( 'Object type.' ),
					'type'        => 'string',
					'enum'        => $types,
					'context'     => array( 'view', 'embed' ),
					'readonly'    => true,
				),
				self::PROP_SUBTYPE => array(
					'description' => __( 'Object subtype.' ),
					'type'        => 'string',
					'enum'        => $subtypes,
					'context'     => array( 'view', 'embed' ),
					'readonly'    => true,
				),
			),
		);

		$this->schema = $schema;

		return $this->add_additional_fields_schema( $this->schema );
	}