It may be free, but it cannot be used without credits.

  Error: {"type":"error","error":{"type":"invalid_request_error","message":"Your credit balance is too low to access the Anthropic API. Please go to Plans & Billing to upgrade or purchase credits."},"request_id":"req_011CaGaBf6uTHfbmdZ39nx1Z"}

Again it is to help prevent abuse I don't really see how this is a valid concern? Tokenization is actually fairly CPU intensive