Howdy folks!

For me, the companion should provide [Enemy Radar] and collect the resources while providing utility during combat. Also it's important to be hard to kill so you won't lose your little helper during the mission.

Let's talk about the mods:

• Primed Animal Instinct + Fetch -> Those 2 give you the ability to see the enemies on the map and grab the loot when in close proximity.

• Link Health + Link Armor -> Boost your Kavat's stats so it doesn't get one shot.

• Primed Pack Leader -> Press E once or twice and your companion will be back to full hp.

• Hastened Deflection -> Since shield gating it's a thing, it's better to have a small shield which regenerates faster instead of a big slow one.

• Tek Assault -> 60% chances to 'cheat death' seems reasonable.

• Mischief -> Another defensive option. It's all about keeping your pet alive. Invisible cats don't get shot so they don't die. :]

• Tek Enhance -> This one boosts the duration of the Kavat's abilities.

• Charm -> Here comes the magic: this thing gives you the "good fortune" aka the buffs (more details below).

***A few words about Shield Gating

Shield Gating is an effect that occurs when shields are fully depleted, which prevents any excess damage leaking into the health pool. Warframes, Companions, and Necramechs gain 1.3 seconds of invulnerability upon hitting the shield gate, only resetting when shields are allowed to fully replenish. If the shield is still in the process of recharging after the gate has activated, the shield gate will only last for 0.33 seconds.

Charm - When it procs, it will give you one of the following:
1) Critical Chance Bonus -> Sets critical hit chance to 200% - 30s duration.
2) Energy Refund -> All energy expenditure from Warframe abilities is refunded for 10 seconds.
3) Doubled Pickups and Affinity -> Any pickups collected or affinity earned are doubled - 120s duration.
4) Instant Reload -> Reload instantly once.
5) Reinforced Shields -> Negates damage received from the next incoming hit. Additionally, awards 150 overshields.
6) Rare Resource -> The Smeeta creates 1 instance of the current planet's rare resources for its owner.

Other viable mods choices:

• Animal Instinct - It can replace Primed Animal Instinct if you don't have it.
• Pack Leader - It can replace Primed Pack Leader if you don't have it. Actually you don't even need the primed version, I used it just because I have it.
• Medi-Pet Kit - The heal is not significant since you have Pack Leader, but the Bleedout Reduction is nice.
• Synth Fiber - Extra armor for your companion is always welcome.
  The damage output of the Smeeta Kavat is not relevant, therefore adding damage mods and Hunter Recovery is not efficient.

Conclusion

Smeeta Kavats are arguably the best companions (also my companions of choice). They provide loot bonuses, critical chance and other helping stuff combat related.
It comes with 2 disadvantages:
1) Buffs are RNG dependant - you need good RNG to get a buff and good RNG again to get the buff you want, but it eventually happens.
2) It doesn't have a self revive option like Vulpaphylas so you must pay attention to their health in arbitration.

Check out my other companion builds:

• Carrier - Your ammo buddy
• Djinn - Self revive companion
• Panzer Vulpaphyla - The Immortal Fox
• Adarza Kavat - Critical Eidolon Hunter