Add an item information and an anvil recipe

Hello,
I'm looking to add enchantments to my mod. I'm almost close to it but I need 2 things before.
At first, I'm looking to add a description to an item, without condition, and with a condition (if the item has a NBT tag)
Second, I'm looking to add an anvil recipe, like to combine 2 things and get a 3rd thing.
If you know how to do it, could you tell me? Even if it requires to touch on code, I can do it, but I need instructions.
Thanks for any help!