Marketing technology is already complicated enough for publishers without having to worry about how advertisers leverage their vendors. But publishers that rely on programmatic advertising would be wise to dissect how their ad partners’ demand-side platforms (DSPs) rank inventory.

Publishers have a slew of their own vendors, so their tech teams may feel too overwhelmed to dig into the mechanics of advertisers’ vendors. For instance, the 500 largest publishers in the US use about six sell-side platforms, according to data from ad tracking firm Pathmatics. However, publishers that ignore the inner workings of buy-side platforms may find that their inventory is being dinged without explanation, since DSPs are one of the most common technologies used by programmatic advertisers, according to a London Research survey of 100 senior ad buyers worldwide.

In March, publisher CafeMedia ran a test with a DSP to see how its inventory was being scored. Instead of being scored per article or per ad unit, CafeMedia found that on metrics like viewability, it was scored by its average viewability rating across an entire website, said co-founder Paul Bannister.

CafeMedia also discovered that when the DSP turned on brand safety filters, the number of bids that came in were significantly cut—even if the content focused on benign subjects such as food recipes.

This is because brand safety tools are designed to be extra cautious so that controversial content doesn’t slip through to pair with brand ads. Because inventory can get miscategorized, it is in publishers’ best interest to adopt brand safety vendors to monitor how their inventory is being labeled, according to Bannister. Publishers can then use this information to advocate for why their inventory should have more favorable scores across various metrics.

“You have to understand how you are being scored, and how the scores will affect you,” Bannister said. “Then you have to talk to your buyers.”