Tags or Prefix not work with REST API

[Askancy]

Hello I was trying to implement the REST API forums/topics POST on my site, I just have a problem... 

If I try to post a new topic WITHOUT the tag or prefix works, but with the prefix or tag no, why?

and it returns me the error: " array(2) { ["errorCode"]=> string(6) "EX1048" ["errorMessage"]=> string(13) "UNKNOWN_ERROR" } "
This is the code I am using:

	var_dump(
		\IPS\Http\Url::external( $url . "api/forums/topics" )->request()->login( $key, "" )->post(
			array(
				'forum'	=> 5,
				'author'	=> 1,
				'title'		=> 'Test titolo discussione',
				'post'		=> '<p>Proviamo se funziona</p>',
				'tags' => 'test'
				)
			)->decodeJson()
		);

If I remove "'tags' => 'test'" it works...

[Askancy]

Nobody ever used the Rest API of IPB?