It's great to include descriptive details, but as with many things in writing, there's a limit to how far you should go. If you include too many details, you run the risk of coming across as pretentious, overly flowery, or writing "purple prose." This becomes very easy to slip into as a fantasy writer, especially if you use a lot of adverbs, flowery descriptions, and metaphors.
I don't think your paragraph slides too far in that direction, but there are some unnecessary descriptive words here. If I was your editor, I would definitely change "headlights in the dying sun" to just "headlights." The former feels a little purple and pretentious to me. (You also have a few grammar and apostrophe issues, but that's not relevant to the question.)
You also have some unnecessary descriptions. "The ground at my feet"? Of course the ground is at your feet - that's where ground always is! Take off "at my feet." And so on. Similarly, you don't need a lot of these adjectives and adverbs. All minivans are "large," and "easily" is not necessary, either.
The point I'm trying to make here is that whenever you can cut out a word without fundamentally changing the meaning of the sentence or the passage, cut it out. This will drastically help with the wordiness of your writing and make it easier to read.
If I was an editor working on your passage, this is how I would revise it.
Its scaly head was easily the size of a large minivan in the shape of a diamond, with a glistening black forked tongue the length of my body. It’s eyes were glowing a yellowish-green like headlights in the dying sun. It opened its mouth, revealing fangs the length of my arms, dripping with inky black venom. It’s mouth was ringed with a crusty brown substance, and with horror I realized it was dried blood. The loudest, most horrible noise I’d ever heard shook the ground at my feet. (88 words)
My shortened version:
Its scaly head was minivan-sized, diamond-shaped, with a glistening black forked tongue the length of my body; its eyes glowed yellowish-green like headlights, and when it opened its mouth, it revealed fangs the length of my arm, dripping with inky black venom. Its mouth was crusted brown, and I realized with horror it was dried blood as the loudest, most horrible noise I'd ever heard shook the ground. (68 words)