Hi @Seunghyun,

This error is likely caused by the Databricks SDK’s authentication step, not by the Service Principals API itself. The SDK is trying to obtain an OAuth token for your AccountClient, the token request is failing, and the error payload coming back from the server doesn’t include the usual error/error_description fields, and so the SDK can only surface it as ValueError: unknown: unknown.

From what I can see, common causes are:

• Using the wrong accounts host URL for your cloud/region (for example, https://accounts.cloud.databricks.com is specific to certain deployments).
• A misconfigured client (service principal)... e.g., not truly account-level, not enabled for M2M, or not allowed on that account.
• General OAuth misconfiguration between the host, account_id, client_id, and client_secret.

Can you check whether...

1. The host value matches your Databricks account console for your cloud/region.
2. The client_id / client_secret belong to an account-level application that’s configured for client‑credentials on that same account.

If this answer resolves your question, could you mark it as “Accept as Solution”? That helps other users quickly find the correct fix.