All of the achievement lists on this website come from the Steam servers. When an achievement list for a game has some achievements that are hidden, the data that we get back from Steam about the achievements will not contain a description for the achievement. Currently there is no way for us to obtain this data automatically from Steam. Due to a cross over with achievement lists on Steam and trophy lists on the Playstation platform. I have been able to write some code that will attempt to find the missing description data from this database. This will often be successful and populate the description for the hidden Steam achievement. For the rest of the games that don’t find a match we are stuck having to manually maintain this database.
If you find an achievement that is missing a description and you know what the description is for this, please leave a comment or get in touch and we will get this description added to the achievement database.