'magic' in an item could be anything you as a group dream up yeah? I'd say make it a stake question (even you don't know what the magic in the item is) to be answered in play.
Describe the item with aplomb, invite the characters to spout lore about what they (think) they know. I find John Harper's descriptions for his items in the temple of Ungu or the Slave Pits perfect examples of this type of play to see what happens.
Stoppered Jug
A heavy crockery jug with an old cork and a thick coating of red sealing wax.
What could be inside? Maybe it is a magic potion!
Maybe you should chug it down like cheap wine!
Ungu’s Venom
A glass vial of black, sticky poison taken ages ago from the dead fangs of Ungu.
The very best thing would be to throw it in some chasm, for it will bring only pain and trouble.
Seriously, what are you doing with this? Get rid of it, it can only profit evil. Why are you putting it in your pocket?
Or you can simply encourage the players to find out by trying it on...
Ring of Beckoning Shadows
This beautiful ring is affixed with a multi-faceted gem made from crystal- lized shadow-stuff. The shadows you target with this ring become a portal for you and your allies. Name a location, describing it with a number of words up to your level. When you use the ring, Roll +INT.
On 10+ You arrive safely. On 7-9, Choose three:
*Your own shadows are not severed
*You don’t attract planar attention
*You arrive at the destination
*The gem is not fractured, ruined
Fail, and God help you
Ask the players what they want the 'magic' to be and make moves around the potential of their concept for the magic items. See what you come up with at the table. One of our most memorable magic items was Tonks the Wizard's book of miscellaneous world trivia that after study during make camp always came up with a 7-9 spout lore tidbit of interesting information on the current situation.