API for label search

Hi Team, I am trying to search all messages in any dashboard through labels; however, don't see any message either through API v1 or v2.

Please find the API which I am trying to use 
https://site/api/2.0/search?q=SELECT subject,id FROM messages WHERE labels.text='GPS_Generic'&restapi.session_key={{tz_session}}&restapi.response_format=json

or 

https://site/restapi/vc/search/messages?q=label.text:GPS_Generic&restapi.session_key={{tz_session}}&restapi.response_format=json

Please let me know is something wrong which I am doing.

Thanks