Ah got it, if it fails even with a single tool, then this points more to a KB indexing/retrieval issue than routing.
That error usually means the files aren’t actually retrievable at query time, even if they show as uploaded, so I’d try re-indexing or testing with a fresh file to confirm.
Also double check the KB is properly attached to that exact tool instance, not just the assistant.
have you been able to get any fileId to return results directly via API?
@lucia