The phrase "a key agent" is correct and usable in written English.
It can be used to refer to an important or influential person or entity in a particular context, such as in business, science, or social dynamics.
Example: "In the success of the project, she was recognized as a key agent in driving innovation and collaboration among the team."
Alternatives: "a crucial player" or "an essential contributor".
Roger Lloyd Pack also makes Buckingham a key agent of Richard's royalist coup and encourages the audience to give him vocal backing.
Everyone involved signed confidentiality agreements that, ironically, commit them to the kind of personal prudence and privacy that Facebook – a key agent of invasion and exhibition – threatens to destroy.
American officials believe that the Pakistani intelligence services, once seen as a key agent in the creation of the Taliban, have been thoroughly reformed since Sept. 11, 2001, and are now committed to fighting both Islamic extremism and terrorism.
As African parliamentarians, we are also faced with an additional challenge, which is to be recognised as a key agent for change by some donors and international organisations, despite the important scrutiny function that parliaments perform.
Among the four arrested but not charged was Omar Mahmood Abu Omar, an Islamic religious leader who American and Jordanian officials say is a key agent for Mr. bin Laden in Europe.
Where the Europe of Jacques Delors appeared to offer some defence against the Thatcherite onslaught witnessed here in Britain, today's EU is a key agent and driver of that neoliberalism.
The type of gasifying agent is a key factor in the determination of the content of the hydrogen product.
It indicated that the concentration of treating agent was a key factor for the textural properties of the modified hierarchical SAPO-11.
All B-vitamins, folate, and folic acid (pteroyl-l-glutamic acid) are beneficial nutrients for optimum productivity in dairy animals, but vitamin B12 is an especially key agent in folate metabolism.
Eve Best - who, like Rea, appeared in The Shadow Line - stars as a key MI6 agent in the Washington Bureau who is at loggerheads with her UK counterparts.
Eve Best - who, like Rea, appeared in The Shadow Line - is also in the series starring as a key MI6 agent in the Washington Bureau who is at loggerheads with her UK counterparts.
