accounts(venue(), credential_id()) ::
  {:ok, [account()]} | {:error, shared_error_reason()}

amend_bulk_orders([{order(), amend_bulk_attrs()}]) ::
  {:ok, amend_bulk_response()} | {:error, amend_bulk_order_error_reason()}

amend_order(order(), amend_attrs()) ::
  {:ok, amend_response()} | {:error, amend_order_error_reason()}

cancel_order(order()) ::
  {:ok, cancel_response()} | {:error, cancel_order_error_reason()}

create_order(order()) ::
  {:ok, create_response()} | {:error, create_order_error_reason()}

maker_taker_fees(venue(), credential_id()) ::
  {:ok, {maker :: Decimal.t(), taker :: Decimal.t()} | nil}
  | {:error, shared_error_reason()}

positions(venue(), credential_id()) ::
  {:ok, [position()]} | {:error, positions_error_reason()}

products(venue()) :: {:ok, [product()]} | {:error, shared_error_reason()}