src/Forms/GridField/SEOEditorMetaDescriptionColumn.php
public function getErrors(DataObject $record)
    {
        $errors = [];

        if (strlen($record->MetaDescription) < 10) {
            $errors[] = 'seo-editor-error-too-short';
        }
        if (strlen($record->MetaDescription) > 160) {
            $errors[] = 'seo-editor-error-too-long';
        }
        if (strlen(SiteTree::get()->filter('MetaDescription', $record->MetaDescription)->count() > 1)) {
            $errors[] = 'seo-editor-error-duplicate';
        }

        return $errors;
    }
public function getErrors(DataObject $record)
    {
        $errors = [];

        if (strlen($record->MetaDescription) < 10) {
            $errors[] = 'seo-editor-error-too-short';
        }
        if (strlen($record->MetaDescription) > 160) {
            $errors[] = 'seo-editor-error-too-long';
        }
        if (strlen(SiteTree::get()->filter('MetaDescription', $record->MetaDescription)->count() > 1)) {
            $errors[] = 'seo-editor-error-duplicate';
        }

        return $errors;
    }
Get the errors which are specific to MetaDescription

@param DataObject $record
@return array