The trading option of some villagers does not correspond to what it should be. In the picture, you can see that this toolsmith does not buy diamonds, while, if I believe the wiki (https://minecraft.gamepedia.com/Trading#Toolsmith_.28black_apron.29_2[]) it shoulds.

I was not able to reproduce it in a flat creative world, and not all villagers have this problem in my save. A librarian has a similar problem: not buying book and ink, not selling compass or clock, and a farmer is not selling cake.

Additionally the toolsmith does not earn any experience from its trade (as you can see when trying to trade the shovel) and hence cannot get the Master rank.

This is a bug observed on a save initialized on version 1.14.4 and updated at each pre-release. I cannot tell on which version the toolsmith appeared, but the librarian definitely appeared on the pre-release 2.

Many thanks in advance for your assistance.