The phrase "tool in one's arsenal" refers to a resource or method that someone has available for use in achieving a particular goal or solving a problem. Full definition
Overall, though, this is a fairly useful tool in the arsenal of an Android enthusiast. (xda-developers.com)
A strongly written resume is one of the best tools in your arsenal for getting the job you desire. (resumehelp.com)
When it comes to marketing your book and truly connecting and communicating with your fans, one of the most powerful tools in your arsenal is an email list of eager and targeted subscribers. (yourwriterplatform.com)