The phrase "a major tool of" is correct and usable in written English.
You can use it to describe something that is an important instrument or method for achieving a particular goal or purpose.
Example: "The internet has become a major tool of communication in the modern world."
Alternatives: "a key instrument for" or "an essential means of".
Posters and public slogans are a major tool of propaganda in the North.
With the city's annual budget already passed, Mr. Bloomberg has lost a major tool of persuasion in his negotiations with council members.
But the inquiry, by the Royal Society, stopped short of recommending mass vaccinations, saying instead that vaccinations should be used "as a major tool of first resort" when foot-and-mouth has already appeared, to prevent it from spreading to healthy animals.
Reserve networks are a major tool of ecological management aiming at biodiversity conservation.
The spatial database of landslides and landslide causal factors to be used in the susceptibility analysis was prepared in the GIS environment, which has been used as a major tool of spatial analysis in landslide studies.
A major tool of the observatory—"We called it that because we are observing carbon with a variety of tools," said Hazen is the diamond anvil cell, which recreates the massive pressures and temperatures found within the planet.
Physical training has been established as a major tool for prevention of the occurrence of a range of diseases and loss of functional impairment as well as rehabilitative approaches such as maintaining autonomy, cognitive performance, and the reduction of depressive mood [ 73].
The kinetic models are undoubtedly a major tool for investigation of biochemical networks [9].
Numerically exact investigations of interacting spin systems provide a major tool for an understanding of their magnetic properties.
The identification of low penetrance genes able to increase the risk of developing cancer could constitute a major tool for the identification of individuals with inheritable altered susceptibility.
Gene expression profiling has become a major tool for the study of breast cancer and substantial amounts of data are available from public databases.
