Why grade labels are unreliable
Japan does not legally define ceremonial, premium, or culinary grade. Brands set their own tiers, so the same name can describe very different teas. Hugo Tea, Mizuba, and Jade Leaf have all written publicly that buyers should look past the tier label.
What to actually look for
A good matcha is vibrant jade green rather than yellow or olive, milled to about 5 to 10 microns so it feels like silk between your fingers, and tastes umami-forward with only mild astringency. Origin should be a single named region in Japan, such as Uji, Nishio, Yame, Kagoshima, or Shizuoka, rather than an unspecified country of origin.
Matching grade to use
Use a top tier matcha for koicha, a drinking grade for usucha, a sturdier blend such as Ippodo's Sayaka or a labeled latte blend for milk drinks, and a culinary grade for baking and ice cream. Drinking a culinary grade plain or whisking a top tier into a sweet latte are both wastes of the leaf.