How do I specify the condition of my item when I list it using the API?
Several categories are requiring that you specify the new, more granular Item Condition values using the new ConditionID field.
To find the right condition ID to use in your listing:
Use Trading API GetCategoryFeaturescall to determine whether ConditionEnabled is set to EnabledorRequired for the category.
If this condition model is enabled (or required), look up the list of valid condition IDs in ConditionValues. Each ID also has a human-readable display name, such as "New" or "Manufacturer refurbished". These are returned in GetItem API, but you cannot pass them in your listing request.
After choosing the most accurate condition ID from GetCategoryFeatures, use Item.ConditionID to specify the condition in listing (or related calls).
Here is a snippet from the AddFixedPriceItem API request that illustrates listing an item with Condition 'New'