1. The first thing your reader sees is your cover letter. Make it work for you. Keep it brief and focused on you as a poet. Don't bother to tell your age (you'd be surprised how many people share this irrelevant information). Also don't list the big name poets you've studied with. Do not be a name dropper!
2. Also do not include in your cover letter any words of praise from other poets or teachers. This will not affect the reader's impression of your work. Definitely do not include blurbs. Why would you already have blurbs, the potential publisher wonders. But feel free to include information about any close acceptances the manuscript has had.
3. If you are asked to provide a description of your manuscript's content in your cover letter, keep that brief and focused. If you find it impossible to describe your manuscript, it's possible that you haven't yet found its center. I see lots of descriptions that list a dozen themes covered in the manuscript: nature, climate change, love, death, religious conversion, pollution, birds, waterways, marriage, children, and so on. Look at that list. Can you find some common themes? Might they suggest a way to t