This place could be perfect: a beautiful building in a garden setting at the foot of Yangmingshan, and at the start of the beautiful historic Tianmu Trail, which offers the chance to see monkeys.
But unfortunately very little if any of the menu is vegan, and if any of it is I couldn't find it, even though I can read and speak some Chinese, and had the translation help from another kind customer who spoke fluent English. I ordered a "Thai" curry (once establishing with the chef that coconut milk was ok, but dairy products weren't) but without the vege prawns, which would almost certainly have contained dairy products. But instead it had tiny pieces of soy ham all through it, which the owner assured me were vegan, but any vegan who lives in Taiwan knows that soy meat is virtually never vegan unless it's from a vegan strictly restaurant, as dairy (and often egg) products are otherwise an essential part of the formula to make it more meat-like. So I just ended up having to carefully pick out all these pieces of soy meat from the curry and the soup which came with the set.
Vegan issues aside, this place is grossly overpriced for what it serves. My meal consisted of a bland "Thai" curry (really just noodles and a few tiny pieces of vegetables - and soy ham - in an insipid coconut milk sauce, some stringy greens, a few mouthfuls of lifeless salad and a tiny bowl of red bean dessert, which was probably the best part of the meal (but would cost about 30NT anywhere else). And that came to 560NT, which would get a feast at other vegetarian or vegan restaurants in Taipei.
By far the best option would be to go to Yummy Vegan House a couple of stops up (Qiyan Station), where you'll get a much better meal for a quarter of the price, or eat in central Taipei before you come. If you must eat dinner in Tianmu a better option would be the Easyhouse Vegetarian Restaurant at the Tianmu Roundabout (above McDonalds!) or else there's a so-so vege buffet (not really worth adding to Happycow) at 32 Tianmu Road (士林區天母西路32號).
Cons: virtually nothing vegan; no way to tell, bland food, Very expensive!