Suppose a level 1 artificer has a hand free and the other wielding a shield.
Can the artificer cast spells without using up their object interaction action?
For most spellcasters, a free hand is enough to cast spells, with no object interaction action required:
Material (M): [...] A spellcaster must have a hand free to access a spell's material components -- or to hold a spellcasting focus -- but it can be the same hand that he or she uses to perform somatic components.
However, the Artificer has a special requirement for their spells:
You produce your artificer spell effects through your tools. 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.
Does this mean the artificer have to spend an object interaction action to wield the tool before he can cast a spell? Or, can the artificer access the tool as part of the spell?