Food diaries fail because they ask for everything. MigraineMe asks for the meal and does the chemistry: every food is tagged for the four compounds that matter most for migraine, so you see the migraine side of a plate before you eat it.

Alcohol was named as a trigger by 38% of patients and food by 27%: common enough to track, personal enough not to guess.
Kelman, Cephalalgia 2007Search the USDA database or scan a barcode. Cheddar, a supermarket cracker, a glass of red: each comes back with calories and macros and, more usefully, with its tags.
Every result is marked for the four compounds, low to high, so a day's log adds up to tyramine high, histamine high before you have had a single symptom. Those tags are triggers, and they get the same statistics as everything else. Red wine, for the record, is a histamine trigger.
Already logging in MyFitnessPal or Cronometer? Connect it and the day's food and totals come across on their own.
Log → Food. Search the USDA database or scan a barcode, and every result comes back tagged for tyramine, alcohol, gluten and histamine on a low-to-high scale, so you see the migraine side of a food before you eat it. Today's log sits under the search, and Monitor → Diet keeps the 14-day history with your migraine days marked.
Nothing, unless you want it automatic. A nutrition app can feed the day in through Health Connect, but it can only be classified when it writes per-item entries with a food name; apps that send daily totals only cannot be tagged. Log the trigger foods by search or barcode and you get the classification either way.
No. Log what you eat when you can. The tags and the correlation engine work with whatever is there, and gaps are simply days without food data.
Tyramine, histamine, gluten and alcohol, each on a low to high scale per food.
Caffeine is tracked as part of diet. Hydration comes from Health Connect only; there is no manual water counter.