User can enter these credentials at the AZ Opportunity settings if he wishes to receive the most accurate data when using AZ Opportunity Gizmo:
Digital signature is used to provide a proof that you truly are a sender of the request. For all requests AZ Opportunity Gizmo calculates the signature using your Secret Key. Amazon uses the Access Key ID in the request to look up your Secret Key and then calculates a digital signature with the key. If the signature that Amazon calculates matches the signature you sent, the request is considered authentic. Otherwise, the request fails authentication and is not processed.
Note that AZ Opportunity Gizmo extension does not store, transmit or share any of your data (including MWS credentials). It is stored locally on your personal computer(s) you use with AZ Opportunity Gizmo plugin.
All additional information on Amazon MWS account and usage can be located by following the link: https://developer.amazonservices.com/gp/mws/faq.html