

See its game statistics in the Steel Defender stat block, which uses your proficiency bonus (PB) in several places.

It's friendly to you and your companions, and it obeys your commands.

These spells count as artificer spells for you, but they don’t count against the number of artificer spells you prepare. Starting at 3rd level, you always have certain spells prepared after you reach particular levels in this class, as shown in the Battle Smith Spells table. If you already have this proficiency, you gain proficiency with one other type of artisan's tools of your choice. When you adopt this specialization at 3rd level, you gain proficiency with smith's tools. Source: Tasha's Cauldron of Everything/Eberron: Rising from the Last War Tool Proficiency
