Hi @run480 , We understand that you are facing the following error while you are trying to access the model serving endpoint with a Service Principal Access Token:

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"This API is disabled for users without the workspace-access entitlement"

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The error message looks like it's because of Missing Entitlement “Workspace access” on Service principle

Can you please check and confirm if the Service principal is assigned this entitlement "Workspace Access" ? 

An entitlement is a property that allows a user, service principal, or group to interact with Databricks in a specified way.

In order to resolve the error, could you please try the below steps

1) Could you please assign entitlement to your service principal?
2) Generate a new token and then try to access it.

Please refer to doc: https://docs.databricks.com/dev-tools/api/latest/scim/scim-sp.html#add-entitlements
https://docs.databricks.com/administration-guide/users-groups/index.html#assigning-entitlements

Please let me know if this helps and try to test and list any other resources using the service principal token you generated.
Leave a like if this helps, followups are appreciated.

Kudos

Ayushi