Its easy to list items on amazon.
If the item is already available on amazon, you can list your article with the ASIN (amazon article number). in this case you don't need to write your own description, you only need to define quantity and price.
If the item is not in the amazon catalogue, you need to list your article with the help of Amazon Flatfiles. In this case you need the UPC, EAN or JAN code. Here you need to write the whole description on your own, product image.....
If your product has no official barcode (UPC, EAN, JAN....), you need to get one!
You are not able to list/sell products without giving it a code listed above.