With the Amazon Selling Partner API (SP-API), a single set of credentials (Client ID, Client Secret, Refresh Token, etc.) is associated with a seller account, not individual developers. The primary user of the seller account creates a Developer Profile and generates these credentials. Multiple developers can use the same set of SP-API credentials to build and test applications. The primary user securely shares the credentials with the development team, and each developer can use them to authenticate and make API requests on behalf of the seller account.

It's important to note that the SP-API credentials are tied to the seller account, and the primary user is responsible for managing and securing them. The development team should follow best practices to ensure the credentials are stored securely and only accessed by authorized developers.

In summary, even though only the primary user can create and manage SP-API credentials, multiple developers can work with the same set of credentials to develop applications for the seller account.