How do you make a tag change phone settings?
Through the automation system your phone already provides, and only for the settings that it chooses to expose. That list is shorter than most people expect, it differs between the two platforms, and it is the constraint that decides what you can actually build.
The automation system does it
The tag holds an identifier or an address. Something on the phone recognises it and performs steps.
That something is the phone's own automation feature, or an application built for the purpose. Either way, the tag contributes the trigger and nothing else.
So the capability question is entirely about what your phone's automation system can do, and a tag adds no settings access of its own.
Only what is exposed
An automation can change what the platform allows an automation to change, which is a deliberate subset rather than everything in the settings.
Volume, brightness, connectivity toggles, focus and do not disturb modes are commonly available. Deeper system settings usually are not.
Anything touching security, permissions or another application's data is generally out, for reasons that are easy to agree with once stated.
Check what is offered before designing a routine, because discovering a missing step halfway through is how these projects stall.
Where the platforms differ
Android exposes more to automation, and what exactly varies between manufacturers, since several add their own automation layer on top.
iOS exposes a curated set through its own shortcuts system, with some actions requiring confirmation rather than running silently.
So a routine built on one platform frequently cannot be reproduced on the other, and a household with both will end up with two different builds.
Take NFC Tools. On iOS it requires an iPhone 7 or later running iOS 15.6 or later, and the app must be launched manually. Background reading is available from the iPhone XS and XR onwards.
Building one
Start from the setting rather than from the tag: confirm the automation system can change it, manually, before anything is written.
Write the tag last, since it is the part that always works and the part that takes seconds.
Test it from a locked phone, from a busy phone, and after a restart, because those are the three states where routines fail.
And keep it short. Every step is one more thing that can be withdrawn by a future platform version.
Frequently asked questions
Can a tag change any setting?
Only the ones your platform exposes to automation, which is a deliberate subset. Deeper system settings are generally out of reach.
Does the tag do the changing?
No. The tag is the trigger and the phone's automation system performs the steps. The tag adds no access of its own.
Will my routine work on both platforms?
Frequently not. The exposed actions differ, so a household with both platforms usually ends up with two separate builds.
Why does a step require confirmation?
Some actions are deliberately not silent. That is a platform decision rather than something a tag can bypass.