When choosing a crafts person to work for you by selecting a registered Artisan you will know that the crafts person is qualified to do the work for you. They work to a prescribed method set by their trade. You have guaranties and insurances to cover the work they do. They will quote for the work they are to undertake so you will know exactly what your quote is for.
It is always best to get recommendations if they are not know to you ask for references and speak to others that have used them. Their paperwork should display their registration number, if in doubt ask to see their registration card or contact the Chambre de Métiers where they are registered.