To retrieve the accessible repositories for a client, download repo/repoindex.xml from the SMT server with the client's credentials. The credentials are stored in /etc/zypp/credentials.d/NCCCredentials on the client machine. Using wget, the command for testing could be as follows:
wget https://USER:PASS@smt.example.com/repo/repoindex.xml
repoindex.xml returns the complete repository list as they come from the vendor. If a repository is marked for staging, repoindex.xml lists the repository in the full namespace (repos/full/$RCE).
To get a list of all repositories available on the SMT server, use the credentials specified in the [LOCAL] section of /etc/smt.conf on the server as mirrorUser and mirrorPassword.