You can authenticate with the vCenter Server Appliance by using a user name and password known to the vCenter Single Sign-On Service.

If you prefer to delegate the process of requesting a SAML token for your API client, you can present your vCenter Single Sign-On domain credentials to the vSphere Automation API endpoint and request a session ID. The endpoint process forwards your credentials to the vCenter Single Sign-On Service and requests a SAML token on your behalf. In this case, you never deal with the token.