The 2019 UA Artificer's Spellcasting feature contains this sentence:
You must have a spellcasting focus—specifically thieves’ tools or some kind of artisan’s tool—in hand when you cast any spell with this Spellcasting feature.
I originally read this as saying that the artificer could use tools as their spellcasting focus, in the same way as a wizard can use a wand or staff. However, on closer inspection, this seems to say that an artificer needs their focus in hand in order to cast any spell, even spells with no material component and spells with a costly or consumed material component that can not be substituted for a spellcasting focus. Which is the correct reading?
For contrast, the wizard's Spellcasting feature has this to say on using an arcane focus:
You can use an arcane focus (see the Adventuring Gear section) as a spellcasting focus for your wizard spells.
And other official classes all have similar rules, differing only in the type of focus mentioned.