add_filter('frm_formatted_entry_values_content', 'show_field_name_in_api_result', 10, 2);
function show_field_name_in_api_result( $content, $args ) {
	$entry_id = 58191; // change 58191 to your entry ID
    if ( $entry_id !== (int) $args['entry']->id || ! is_array( $content ) || 'array' !== $args['format'] ) {
		return $content;
	}
	$field_keys = array_keys( $content );
	$fields = FrmField::getAll( array( 'field_key' => $field_keys ) );
	$output = array();
	foreach ( $fields as $field ) {
		$output[ $field->name ] = $content[ $field->field_key ];
	}
return $output;
}