They have to authorize it for the Constitutional power they have to be observed.
The formal/legal declaration need not say “this is a declaration of war” - there is no requirements under the Constitution for any such specific language. But it is an absolute requirement.
Congress shall have the power.... to declare war.
Nobody else has that power under the Constitution.
It is an absolute.
It is a necessity.
The language it consists of is entirely optional.
Founders give a detailed paper trail on why and how Congress should be the only Body to decide military action.
Executive Branches think they are above Congress concerning Article One Section Eight as well as think they only have the power to control "conflict".
Conflicts become all out war while Congress and the executive Branch play political games
War Powers Act tries to stop this corrupt nature of putting Americans in harms way and draining resources.
In the end, we would not need all these laws if Madison and Jefferson along with many more individuals who played a part in the United States Charter, were actually listened to and not ignored by Central Planners.
In the end we are all