Would you agree that the poem "The Eagle" is not a mere description?

I do agree that "The Eagle" isn't mere description. It if were, it is unlikely that we would care very much about reading it, especially nearly two hundred years after it was written.

The point of poetry is to convey experience, and "The Eagle" very much does this. It helps us to see and feel and understand the awful power and majesty of such a predator. One so powerful that it is often alone because...

I do agree that "The Eagle" isn't mere description. It if were, it is unlikely that we would care very much about reading it, especially nearly two hundred years after it was written.

The point of poetry is to convey experience, and "The Eagle" very much does this. It helps us to see and feel and understand the awful power and majesty of such a predator. One so powerful that it is often alone because it can do what many other birds cannot: fly higher, dive faster, hunt better. We can see what the eagle sees, visualize his speed, marvel at the color of the sky around him, so high up.

However, this doesn't really seem like enough either. When we look deeper at the poet's word choices, it becomes clearer that the poem isn't just about an eagle. It can refer to any being that possesses absolute power. The fact that Tennyson describes the eagle's talons as "crooked hands" helps us to discern the fact that the eagle could refer to a person too. He might be an absolute ruler, a tyrant, who holds on to his power by any methods necessary, including corrupt ones.  "Crooked" can mean bent (like an eagle's talons would be) or corrupt (in the sense of, for example, a crooked politician). Further, the fact that the eagle "clasps the crag" indicates that he holds tightly to it, the way such a leader would cling possessively to his power. He "stands" tall, far above everyone else; this "everyone else" is represented by the "wrinkled sea" that "crawls" beneath him (he has all of the power and they have none, as indicated by the word "crawls") (4). He watches all of them, for now, but when he loses power (i.e. when someone overthrows him), he will fall quickly and violently, "like a thunderbolt" (6).  No supreme leader ever "falls" from power softly and gently; it is always a violent revolution or coup that swiftly deposes him. Therefore, "The Eagle" is more than mere description: it conveys experience and creates a symbol for any supreme leader and his inevitable fall from power.