Tau. supports 218 Apple Health metrics, plus 5 profile characteristics and one metric for each medication you share on iOS 26. Every one of them can be browsed in the Data tab, selected, exported, and put in front of the AI. This is not a curated subset — it covers virtually everything your Apple Watch, iPhone, connected devices and health apps record.
Most AI health apps expose a curated shortlist — the thirty or so metrics that make a good dashboard. Tau. takes the whole Apple catalog instead, because the questions worth asking are the ones that cross categories. "Why was my sleep off last Tuesday?" is not a sleep question: it needs that night's heart rate and HRV, the previous day's exercise minutes, the caffeine logged at 4pm, and how much daylight you got. Cut the catalog down and you don't lose a few obscure metrics — you lose the answer.
The 218 are not just a chat feature. They are the same catalog the Data tab displays, the CSV and PDF exports draw from, and the Analysis tab runs its statistics over. Adding a metric adds it everywhere at once.