Global rarity on achievements

[pradella]

Does anyone know how the achievement rarity can be retrieved?

The endpoint users/xuid({xuid})/achievements when using "X-XBL-Contract-Version" = 3 it returns the rarity object; but it seems not accept the titleId param (to filter a specific title)

"rarity": { "currentCategory": "Rare", "currentPercentage": 1.5 }