A "convenient tool" refers to a useful device or item that is easy and effortless to use, making your tasks or activities simpler and more efficient. Full definition
The breath is the most convenient tool for getting into the present moment, and it is always with us — it is a direct mirror of your state of mind. (mindbodygreen.com)
Many issuers also offer convenient tools to save users valuable time, help them stay current on their payments, and avoid penalty interest and negative impact on their credit score. (lifeoncredit.ca)