The phrase "the key tool" is correct and usable in written English.
It can be used to refer to an important tool or item that is needed in order to complete a task, achieve a goal, or resolve an issue. For example, "Education is often seen as the key tool in helping to reduce poverty."
The program is the key tool to building up an ongoing dialogue with them".
Then they whip out the key tool in their monetary policy arsenal – interest rates – and adjust it accordingly.
The focus by rich countries on aid as the key tool to help end poverty needs to be urgently questioned.
Microsoft's restrictive contracts with personal computer makers were the key tool in its campaign to illegally defend its monopoly, the appeals court ruled.
But the explicit reference to monetary policy, rather than the general terms mentioned in September, suggested that the group regarded that as the key tool for more tinkering.
Malcolm Turnbull's claim that coding is the key tool to unlock future prosperity for Australia might sound visionary, but it's not supported by the economic data.
And there were other, not particularly altruistic imperatives: the cold war had begun, and "aid", writes Moyo, "became the key tool in the contest to turn the world capitalist or communist".
Reacting to news of the halted trial, the director general of the UAC, David Kihumuro Apuuli, said behavioural change would be the key tool in Aids prevention in the coming years.
Malcolm Turnbull, not to be outdone, the next day said: "If we want to succeed, and continue to succeed as a prosperous first-world economy... the key tool for that is coding".
Nicholson explained that competition, the key tool, allegedly, for improving quality, increasing productivity, driving down costs and widening choice for patients, is itself proving an expensive impediment to change as lawyers battle over the details of competition law and procurement on a "scale and nature" never anticipated.
Fourth paper is on the key tool of topology optimization, the parametric level set method.
