In the OCI specification there is handling for how the suppliers when site knows where to send the shopping basket data back. This is called the hook_url or return URL. This is configured in the external catalog in AX and used when the user punches out from the procurement site over to the suppliers site.
In this video we walk through the setup of this and how it’s used as it can very supplier to supplier if they choose to change what this parameter is.
Note the parameters you can find reference in the documentation see this previous post.