Subscription for a single month

I am building a paid online tool where you can subscribe for one month without auto-renewal. If you want to use a tool again, you pay one more time.

Is such payment still called subscription, or is there a more precise word to call the payment and the according section in the menu?

Subscription means the right to receive something for a pre-arranged period of time typically for a prepayment.

While we usually assume it's an ongoing arrangement (e.g. month-to-month) it doesn't have to be.

Websites, by their nature, aren't episodic. So, subscriptions describe ongoing access.

Just as a six-month subscription would mean access for 6 months, a one-month subscription would mean access for one.

But, if you wish to remove ambiguity, you can always just call it a one-month membership. To remove all ambiguity you can say in parentheses non-renewing.