function mytheme_preprocess_field(&$variables, $hook) {
$element = $variables['element'];
$bundle = 'my_bundle'; //Do this for only specific node bundles
if ($variables['bundle'] == $bundle && isset($element['#field_name'])) {
$field_instance = Drupal::entityTypeManager()->getStorage('field_config')->load('node.mcdataset.'.$element['#field_name']);
if (!is_null($field_instance)) {
$fieldDescription = $field_instance->getDescription();
if (!is_null($fieldDescription)) {
//Popover works with bootstrap
$variables['items'][0]['content']['#suffix'] = '<div class="tooltip-wrapper"><span class="tooltip-info" data-toggle="popover" data-trigger="hover" data-placement="top" data-content="'.$fieldDescription.'">!</span></div>';
}
}
}
}