The list of vendors generated for the Invite Vendors Recommendation Engine is generated via Commodity Codes. If a vendor has a Commodity Code that matches the opportunity's commodity code they will show up on this list.

NOTE: The Recommendation Engine is useful for making relevant vendors aware of your opportunity, however for best results please ensure that you have assigned the correct Commodity Codes to your project otherwise this can irritate vendors who feel that your project doesn't fall within the scope of their offered goods/services.