You should write everything relevant to the items description. For example If the item has any small details. It is advised to mention the color of the item, as the picture can look different. For instance dark blue can look black in a picture.
The buyers are often asking more details on the sizes for especially adults clothing. It is advised that you give full size detail whenever possible, you can even measure the size yourself if needed. Such measurements should be noted as self taken.
For instance it’s good to measure the inner length of a shoe and add it to the description.
The buyers will make their decision based solely on the information given. It is a good practice to think if you would buy your own item with the information you’ve given.
Any defects should also be noted precisely and truthfully. If the item does not match the given description the buyer can return the item and in such cases you won’t be receive sales credit for the item.
You can add multiple pictures of the item, if there are any defects you should take a picture of those as well.
If there are any pets in your household, those should be mentioned in the description.