@SS In mrityunjaya mantra all tags are useful:
1) Shiva : because devata of the mantra is Shiva.
2) Veda : because it is mantra from Veda.
3) Purana: because the origin and meanings of mantra are described in Purana.
4)Mantra: because it is a mantra
5) Scripture: question is such which answer can be found in Hindu scripture. It's not like biography of saint like question...
So, all tags are fine. If someone wants to add another useful tag then only he can remove one of these (which is less relevant). It isn't necessary to remove unless there is need to use useful tag...