What an agent does
What does a literary agent actually do for you?
An agent submits your manuscript to traditional publishers who will not read submissions from authors directly, negotiates the contract, and takes 15% of your domestic royalties for doing so. That is the whole value proposition. If your goal is a contract with Penguin Random House, HarperCollins, Simon & Schuster, Hachette or Macmillan, you need one.
If your goal is anything else, such as selling on Amazon, reaching readers worldwide, building royalty income or establishing your authority, an agent plays no part. Agents receive no commission on self-published royalties, and they cannot get a book onto KDP or IngramSpark any faster than you can.