Can a tag log something automatically?
It can record that a tap happened, at a time, at a place. That is less than a measurement and considerably more than nothing, and understanding which of the two you need decides whether a logging tag helps you or produces a file you never open.
What actually gets recorded
A tap, a timestamp, and which tag. The phone knows all three and can write them somewhere.
The tag itself records nothing. It has no clock, no memory of being read, and no way to report anything later.
So a logging tag is a button that leaves a trace, and the trace is created by the phone rather than by the object.
Some chips carry a counter that increments when read, which is the nearest thing to on tag logging and requires reading the tag back to consult.
Where that is enough
Habit tracking, where the fact of doing something is the whole record: took medication, watered the plants, fed the animal, went for a run.
Shift or presence marking, where a tap at a place is exactly the evidence wanted.
Anything you currently do not record because writing it down is too much friction. That is the case where a tag genuinely changes behaviour.
And anything where the count matters more than the detail.
Where it is not
Anything with a value: a weight, a reading, a temperature, a quantity. A tap carries no number, so the value has to be typed and the tag has saved you almost nothing.
Anything requiring a note, for the same reason.
Anything you might do without the phone, since the log then has gaps that look like not doing it.
And anything somebody else in the household also does, since the log lives on one phone and records only that person.
Building one that lasts
Log somewhere you will actually look, which is usually an existing application rather than a file created for the purpose.
Confirm the tap visibly, because a log entry you cannot see is a log you stop trusting.
Put the tag exactly where the activity happens, since a log entry made later is worth less than the friction it saved.
And decide in advance what you will do with the record. Logging that changes nothing is a habit that fades within a month, which is the fate of most tracking of any kind.
Frequently asked questions
Does the tag store the log?
No. The tag has no clock and no memory of being read. The phone creates and stores the record.
Can I log a value like a weight?
Not from the tap alone, since a tag carries no number. You will type it, which removes most of the benefit.
What is a read counter?
A chip feature that increments when the tag is read. Consulting it requires reading the tag back, so it suits a tag you keep.
Why do people stop using logging tags?
Because the record changes nothing. Decide what you will do with the data before building the habit.