Could the action, speaking the command word, be a bonus action? the wording seems a bit ambigious on that point. thoughts? 

Quote from Wellthatwasanat1 >>

This item is so useful for warlocks. If you have a 7th level warlock, this pearl, and a rod of the pact keeper, you can basically gain a 3rd and 4th level spell slot after expending your original slots. It's a lifesaver if short rests are scarce. 

 Wait, will that work?  At level 7, you have 2 spell slots that are 4th level.  You don't have 3rd level spell slots to regain.

Quote from Passero_Robotico >>

Quote from Wellthatwasanat1 >>

This item is so useful for warlocks. If you have a 7th level warlock, this pearl, and a rod of the pact keeper, you can basically gain a 3rd and 4th level spell slot after expending your original slots. It's a lifesaver if short rests are scarce. 

 Wait, will that work?  At level 7, you have 2 spell slots that are 4th level.  You don't have 3rd level spell slots to regain.

 Yes. While the Warlock level 7 or higher doesn't have 3rd level spell slots to regain, the Pearl specifically grants a 3rd level spell slot if the slot they're trying to recover is higher than 3rd (which their Pact slot is).

In fact, as-written, a traditional spellcaster can use the pearl even if they haven't used any 3rd or lower spell slots. As long as the user has used a spell slot, and the target slot is 4th level or higher, the pearl grants an "extra" 3rd level slot. (Though there's very little reason to do this.)

Quote from Varax_Abras >>

Could the action, speaking the command word, be a bonus action? the wording seems a bit ambigious on that point. thoughts? 

No. It specifically says "use an action". An action is an action. A bonus action is not an action. There's nothing ambiguous about it.

Quote from ignytezero >>

While it's easy to see the RAI written into this item, as per RAW it is utterly broken and mechanically confusing. I suggest the following re-wording to correct it into be written as per RAI. Yes, more text but also more accurate text.

Pearl of Power
Wondrous Item, uncommon (requires attunement by a spellcaster)
While this slightly shimmering pearl is on your person, you can use one action to speak its command word and regain one expended spell slot up to 3rd level. If the expended slot is of 4th level or higher the regained slot counts as only 3rd level in regards to spellcasting until expended or a long rest. A Warlock able to cast level 4 spells will when casting from this regained spellslot cast it at spellevel 3 instead of max spellevel. Once you have used the pearl, it cannot be used again until the next dawn.

 

 
I don't see the necessity. The text clearly states 'If the expended slot was of 4th level or higher, the new slot is 3rd level.' That covers all spellcasters.

original wording says, if the spellslot being regained is lvl 4 or higher, it only counts as a 3rd level spellslot... so while the pearl can be used on a lvl 4 or higher slot, you do not count the regained slot as such until you have used it at a lvl 3 slot (after regaining it via the pear) or have taken a long rest...

I smell fireball spam…

Only the warlock regains spells and they are all same lvl. The warlock who can tune to 3 items can cast 2 spells and will at lvl 20 be maxed at 5th lvl. Bruh just don't be that guy.

A warlock might squeeze a bit more life out of before outgrowing it, but most casters should have better uses of their attunement slots and Action economy after Tier 1.