Q:

Is the rarity of this homebrew Haunted Staff appropriate?

I'd appreciate an assessment of whether this homebrew staff is rated appropriately.

Haunted Staff
Staff, rare (requires attunement)
A face is carved near the top of the staff, and every time you look
away and look back the face’s expression changes subtly. The staff’s
previous owner has died and chosen to remain in what had been his
focus staff rather than depart for the afterlife.
The soul in the staff can telepathically communicate with you while
you hold it. You can’t prevent this telepathic communication. It would
be nice if you could, the soul spends most of its time reminiscing
about its youth or quietly snoring.
Fortunately, the soul haunting the staff spoke all standard and
exotic languages (BR pg 36). The soul can read with your eyes,
hear with your ears, and translate for you. You gain the benefits of
the Comprehend Languages and Tongues spells while holding the staff.
You also have advantage on Arcana and History checks while holding the
staff.

A:

Rare is appropriate
Being basically a sentient item does not seem to add any detrimental effects (other than annoying the user which does not influence the game mechanic), so we'll ignore it for the analysis of the power of the item.
This leaves us with the following properties:

Cast Comprehend Languages (1st level spell) at will (not really, but this would have the same effect)
Advantage on Intelligence (Arcana) checks
Advantage on Intelligence (History) checks

The ability to cast a spell at will puts this item at rare or rarer.
DMG, p. 285

Maximum Spell Level. [...] A rare, very rare, or legendary item might allow its possessor to cast a lower-level spell more frequently.

Checking the DMG for items providing similar benefits and also require attunement we can find

Belt of Dwarvenkind (rare)[DMG, p. 155]
[Assuming non-dwarven users]

CON increase by 2
Advantage on Charisma (Persuation) when dealing with dwarves
Advantage on saving throws vs Poison
Resistance against Poison
"Cast Darkvision (2nd level) at will (targeting self only)"
Gain language Dwarven

This seems about the same powerlevel, if not more powerful than your item: The advantage on Persuation is more situational, but the effects regarding poison are more powerful than advantage with skill checks for one skill. Restricting the target of a spell to self only wouldn't make this a cantip, so assuming the power of a level 1 or 2 spell there would be appropriate.
There's also the bonus to CON.

Rod of Alertness (very rare)[DMG, p. 196]

Advantage on Wisdom(Perception) checks
Advantage on Initiative rolls
Cast 3 first level and one second level spell at will
Protective Aura

This is clearly more powerful than your item. Making rare an appropriate rarity.

