> grep minimum api/classes/CAction.php
self::exception(ZBX_API_ERROR_PARAMETERS, _s('Action "%1$s" has incorrect value for "esc_period" (minimum %2$s seconds).', $action['name'], SEC_PER_MIN));
self::exception(ZBX_API_ERROR_PARAMETERS, _s('Action "%s" has incorrect value for "esc_period" (minimum 60 seconds).', $action['name']));