The phrase "are the key agents" is correct and usable in written English.
It can be used when discussing important individuals or entities that play a significant role in a particular context or situation.
Example: "In this study, we will explore who are the key agents influencing climate change policy."
Alternatives: "are the main players" or "are the primary actors".
Teachers are the key agents in ensuring that this is the case and young people must be sure of equality and acceptance in the eyes of their educators.
But spiders are the key agents and they have now clothed our entire landscape in a silk garment: all Britain, perhaps, as one single glittering weave.
Engineers are the key agents in the promotion of cost-recovery policies in the efforts to deliver services more 'efficiently'efficiently
Rumen bacteria and fungi are the key agents to degrade plant fiber [2], [30].
Both classes of regulatory proteins bind to specific sequences contained within enhancers, which are the key agents of gene regulation in higher organisms.
For example, there is a wealth of evidence indicating that parents are the key agents in seeking services and initiating treatment for their children as well as contributing greatly to long-term treatment effects (Kazdin 1998; Logan and King 2001; Phillips et al. 2000; Yeh and Weisz 2001).
Their uninspired monikers aside, all of these plans share one defining feature: doctors are to be the key agents of change.
By using an evolutionary analysis of the spatial structure of the waterfront landscape, it demonstrates that government development agencies and event tourism have been the key agents of change in influencing its redevelopment at different phases.
The British allowed this profound belief to be maintained, and Lawrence was the key agent in its propagation and in reassuring the Arabs.
That's the key agent of change".
This supply of riverine sediment has also been the key agent in mediating human occupation of the Mediterranean's clastic coasts.
