Regarding the provision of paid tools using the API, Article 10 (Forbidden Actions), Section 4 of the Terms of Use corresponds.
Users shall not engage in any of the following acts.
(4)To gain income by using the Web Services in ways other than Rakuten Affiliate (excludes the cases where the Company explicitly grants permission)
Use of the API for any purpose other than as an affiliate to earn commissions from tool sales is a violation of the Terms of Use.