What can an NFC tag control at home?
Whatever your home system already exposes to your phone, and nothing more. The tag adds a place and a gesture. If your system cannot dim a lamp from an app, no tag will make it, and if it can, a tag can start that in one touch.
The chain of four
Tag, phone, home system, device. Four links, and the tag is the shortest one.
The tag says which action. The phone recognises that and asks the home system. The system decides and tells the device. The device does something.
Every capability lives in the last two links. The first two decide only how the request is made.
So the question is never what a tag can control. It is what your home system already controls, and whether a tap is a better way to ask.
What the tag actually adds
A place. A tag by the front door means something a shortcut on a home screen does not, because it is where you already are.
A gesture, replacing unlock, find, open, navigate, tap. That sequence is short enough to seem trivial and long enough that people stop bothering.
Availability to other people, since a guest without your applications can still tap something if it opens a page.
And a physical object with a name on it, which is easier to explain to a household than a routine nobody can see.
Where the chain breaks
The phone, if it is asleep, locked, or belongs to somebody without the application.
The connection, since most home systems route a request through a service even when both devices are in the same room.
The home system itself, when a platform changes, an account expires or an integration is withdrawn.
Not the tag. A tag holding a short address is the most durable component in the chain by a wide margin, which is worth remembering when something stops working.
Where to start
With something you do daily and already find slightly annoying. Not the impressive one.
With an action your system already performs reliably from its own application, because a tag will not improve an unreliable action.
In a place you pass anyway, at hand height, on a surface that is not metal.
And with one tag rather than six. The household will tell you within a fortnight whether it was worth it.
Frequently asked questions
Can a tag control a device directly?
No. The tag tells the phone, the phone asks the home system, and the system controls the device. The tag adds no capability.
Do I need a smart home hub?
You need something that can already perform the action from a phone. Whether that is a hub or an application depends on your equipment.
Will a tag work if my phone is locked?
Often not. Tag reading generally needs an awake device, so a tap on the way past a sleeping phone in a pocket does nothing.
Which automation should I build first?
Something you do daily and already find annoying. Impressive automations are abandoned and boring ones survive.