Q: I have previously granted MWS access to my Amazon Selling account to a third-party solution provider. How do I identify and manage 3rd party developers connected to my Amazon MWS account?

Visit the User Permissions page on Seller Central as the primary user. Under Amazon MWS Developer Permissions you can view a list of developers who are currently authorized to use your account. To remove access for that developer, click Revoke under the Action column next to their name.


Source: https://developer.amazonservices.com/gp/mws/faq.html