The Essay

Adjectives describe nouns.

Adverbs describe verbs.

(A complete lesson on adjectives and/or a complete lesson on adverbs might be helpful if you need a refresher on some of the grammatical terms associated with descriptive words.)

There's nothing inherently wrong with describing nouns and verbs, but generally, the best and most vivid writing avoids overuse of adjectives and adverbs.

For one thing, adjectives and adverbs are often vague. A building may be tall, a book long, or a conversation interesting, but those are weak descriptions; they convey almost nothing valuable to a reader. How tall are we talking? The tallest in the city or the tallest in the country or the tallest in the world? How long is this book? Long for a novel, like (Eleanor Catton's) The Luminaries, or long for a poem, like (Walt Whitman's) Leaves of Grass? Was the conversation hilarious, did you learn something you'd never learned, was your interlocutor insanely charismatic? Tall, long, and interesting give us few details, and, consequently, are wasted words.

Consider also the difference between describing Superman as "fast", versus "faster than a speeding bullet". The single, static word "fast" doesn't provide a frame of reference, and the reader is left to try to figure out exactly how fast this fella flies. On the other hand, "faster than a speeding bullet" conjures an image that helps the reader calibrate Superman's flight speed with a known quantity.

Generally:

Avoid vague descriptions.

Perhaps worse than using too many descriptors in general is using too many descriptors in a row. You might be proud of your "neatly manicured green lawn" or gush endlessly over your "friendly big red dog", but in general, it's best avoid repetitive and multiple-vague descriptions.

Interestingly, though it's largely an unwritten rule, we prefer a certain "Order of adjectives", as the Cambridge Dictionary discusses. For example, we comfortably hear "big red dog", but "red big dog" sounds preposterous. (Remember previously we considered the importance of cadence. This is related.)

To illustrate, consider the use of descriptive language in these two passages:

Passage 1: Raymond trotted happily down the steep stairs to his new red bicycle. He donned his jet black helmet, ready to zip to the friendly neighbourhood ice cream shop, where he exchanged a few dollars of his allowance for a delectable, soothingly-cool scoop of chocolate ice cream in a crispy waffle cone.

Passage 2: Raymond walked down the stairs to his bicycle. He put on his helmet and rode to the ice cream shop, where he bought a chocolate ice cream cone.

There's no doubt that Passage 2 is sparse, but as Mark Twain once quipped: "As to the Adjective: When in doubt, strike it out". 

One might think that Passage 1 is more vivid in its description, and therefore preferable to the austere Passage 2. On the other hand, Passage 1 leaves little space for the reader to read creatively.

When writing descriptive prose, consider that:

Reading is a creative pursuit.

As we said earlier, readers read with their own style just as writers write with their own style. Reading, we might say, is a performance akin to public speaking -- though essentially private. Passage 1 obstructs the reader from crafting a personalised moving picture of the action, and to obstruct the reader this way is to squash part of the joy of reading.

Perhaps Passage 2 is simply too sparse. Of course, the example is exaggerated, so you might judge that it needs additional descriptive language. That's fine. The level of description you choose is ultimately up to you, but be aware that, in general, readers react poorly to being squeezed out of their reading experience.

As a final point on the distinction between the two passages: Passage 1 focuses on description; Passage 2 focuses on action. In some circumstances, when appropriate to focus on description, a judicious use of extra adjectives is reasonable. However, especially when action is your focus, limiting descriptive words is the best course. We will say more about this when we discuss verbs.

In the next reading, Virginia Woolf describes the streets of London without overusing adjectives and adverbs. Hers is an active tale of a journey with a purpose: to procure a pencil. To that we now turn.