1. The "Quality Score" & Service Metrics

Cassini (eBay's AI) assigns your store a hidden "Quality Score." This isn't just feedback. It's based on your Service Metrics. If your "Item Not As Described" (INAD) returns are "Very High" compared to peers, eBay penalizes you with an extra 5% Final Value Fee and buries your listings.

The Fix: Under-grade your items. If a shirt is 9/10, list it as "Good," not "Excellent." Surprising a buyer with quality builds trust; disappointing them destroys your algorithm score.

2. Terapeak: The Data Weapon

Stop guessing prices. Use eBay's internal tool, Terapeak. It shows 365 days of sold data.
The Strategy: Look at the "Sell-Through %" column. If an item has a 10% sell-through, you must price it in the bottom 10% of active listings to move it. If it has a 90% sell-through, price it at the top. Market demand dictates your pricing power.

3. The "Z-Curve" of Traffic

eBay traffic is not linear; it follows a "Z-Curve." You get a boost when you list (New Listing), a slump for 30 days (The Valley of Death), and a boost right before the item ends/renews (Ending Soon).

The Protocol: Never let an item sit in the "Valley" for more than 60 days. End it. Use "Sell Similar." This resets the Z-Curve, giving you a fresh "New Listing" boost immediately.

4. Item Specifics = SEO Filters

Buyers use left-hand filters (Size, Material, Sleeve Length) to shop. If you leave "Sleeve Length" blank, and a buyer filters for "Long Sleeve," your item disappears. It doesn't matter if "Long Sleeve" is in your title. The filter relies on the Item Specifics fields. Fill out 100% of them to ensure you appear in every filtered search.