In my community, many application of Tool Belt are told and I introduce some of them.

Practical applications:

• Twice usage of sloted/exhausted tools in single slot: Put two tools, one in play area and the other attached in Tool Belts. After trigger first one, swap it with that in Tool Belt and use one more.
  • Example: Lockpicks, Mariner's Compass, Riot Whistle...
• Fight/Investigate flexiblity for tools: Unlike other classes, some of tool is (two-handed) weapon. When you need to fight, use tool weapon; when you need to investigate, use tool for investigator.
  • Tool weapon: Chainsaw, Sledgehammer...
  • Tool for investigation: Old Keyring, Flashlight, Mariner's Compass, Magnifying Glass ...
• Keeping sacrificial asset: After fully uses of supplies (or any other), attach that asset into Tool Belt and throw it away when you meet asset-hate encounter such as Crypt Chill.
  • Rule note: you still can choose the card attached into Tool Belt because 1) it is still asset 2) you still have the control of it 3) it is still in play. (not official ruling, but my interpretation)
  • Old Keyring: If you investigate using Old Keyring with 1 key, you can attach that at during the investigation test. Nevertheless, the test works normally and the last key is removed from that Old Keyring; however, attached Old Keyring is not discarded because the text box is alread blanked so that the effect "If there are no keys on Old Keyring, discard it" does not work. If you want to discard that Old Keyring for some reason, you simply detach it, and then that is discarded. (my rule interpretation)

Funny(?) applications:

• We can make charged Old Keyring with keys having some secrets (in the Tool Belt), since the "Uses (2 keys)" is blanked. Of course, we should distinguish them even if same resource tokens are placed. After that Old Keyring is detached, it's not clear that the charge and secret could remain on it :)
• Attaching Quickdraw Holster with .32 Colt: We could attach Quickdraw Holster thanks to the existance of the Devil from Observed. Then, .32 Colt in Quickdraw Holster now regain hand slot in the Tool Belt :)
• Discarding (non-slot?) tool card: The common way to discard the asset is using the slot limit, but we cannot do this for non-slot asset so that it's hard to discard non-slot asset. Now, if we want to discard non-slot tool, just attach Tool Belt and then discard (or Sleight of Hand) Tool Belt. Is it really useful? Not yet, because non-slot tool is Darrell's Kodak only when I write this review.

I think Caught Red-Handed is wrongly designed weakness. The effect commonly make the player angry. Why? This has two main effect:

1. Ready each enemy at your location or a connecting location.
2. Each hunter enemy at a connecting location moves 1 location toward you.

However, the discard condition only refers "second" condition. Even if the first condition met, Caught Red-Handed is returned to the deck after making all enemy ready. Notice that it's very easy to meet first condition; whereas it's rare to meet second condition.

Finn has free evade action. Thus, it's very common that he has Pickpocketing. After he evade an enemy, he trigger the Pickpocketing, and draw card. What if that card is Caught Red-Handed? Just evaded enemy is ready! In general, no hunter enemy moves so that Caught Red-Handed is returned into his deck. Now, Finn wasted evade, card. However, the weakness is still in deck.

Captivating Discovery is one of the fascinating card which is spoiled in scarlet keys. This provides the 6-cards searching effect, which helps to trigger the Astounding Revelation. In addition, this gives the 2/4/6-card drawing effect among 6-cards, which is powerful search/drawing ability. Someone might think that dropping the clues is expansive cost. Unlike other clue dropping cards such as Forewarned, however, the player can easily control the timming of the playing Captivating Discovery because the drawing effect is independent to the location. Thus, you could select the location to drop the clues. You may drop the clues at the location with low should value. You may drop the (unnecessary) clues at the location with non-victory location. It means that the cost of "dropping the clues" for Captivating Discovery is commonly lower than that for any other cards.

Just going to drop the Additional Cost ruling here. In particular :

Additional costs do not have to be paid when a Forced effect or mandatory instruction (such as in the Campaign Guide, or on the back of an Act or Agenda card) requires an investigator to resolve an effect.

So if you were torn away forcibly from or to the location with the barrier, you just go. You are not forced to test, and therefore you cannot get to the discard/milling/cancel movement clause. e.g. You cannot use this to your advantage to purposefully fail the test and choose "cancel the effects of the move" to refuse to go/move away. (I did that in one play, kind of amusing the investigators are holding onto the barrier that was harming them earlier, lol)

Disclaimer: Pre-Scarlet Keys release review.

Another niche card that is a bit hard to understand for now. Tactic is one of the least interesting Trait since it only matters for Mark Harrigan but he already accesses 0-5, Chuck Fergus (so "Skids" O'Toole) but it's already fast and doesn't involve a test, Directive - Red Tape but again it's already fast and Sleuth but it's probably one of the least interesting 3-class talent.

So, why would you ever use this card??

The main issue is "At the end of the round", meaning after the enemy phase.

• Daniela Reyes can automatically evade an enemy with her . Trigger it with the Mechanic's Wrench and attack with it, applying the wound. Since your turns are often a bit empty, applying a DoT to an enemy and leaving to engage another one is potentially really good. And on top of that, lvl 0 cards are not so hard to slot in her.
• Survival Knife (0) if, for some reason, you are already considering getting some hits, you can now do so with a 3-hp enemy and kill it after you get attacked. It's not great, but if you planned on taking the Survival Knife already, then it's worth considering.
• Butterfly Swords allow you to perform the first attack on an enemy and the second on another one. So you could technically do the smaller attack combined with Grievous Wound on a bigger enemy and the 2-damage attack to defeat a 2-hp enemy and evade the wounded enemy. That is a veeeery niche situation since it requires you to have 2 enemies in play, one that justifies this and that you are able to evade after... Let's see what other cards come in this pack. As of now, I see an opportunity here, but not enough yet for something viable.
• As suggested in the comment by @Veronica212, "Skids" O'Toole could be somehow a bit interested, as he is more able than others to evade and leave the DoT behind. Cheap Shot (2) is a good way to add 1 damage and exhaust, and Switchblade, Enchanted Blade without using a charge as suggested. It doesn't save you much time unless you can change location and the enemy is not a hunter.
• In the same vein, William Yorick could see use with Stunning Blow, attacking with a Gravedigger's Shovel, Fire Axe without going down to 0 resources, Meat Cleaver without spending the Horror, etc... The problem is that you need both Stunning Blow and Grievous Wound in your hand at the same time, which can be complicated with the little Draw ability of Yorick.
• Honorable mention to Trusty Bullwhip would have been nice with this since you can attack, exhaust to evade and apply the bleeding.

Conclusion: As of now, except for Daniela Reyes, I wouldn't really consider this card yet, but that may change in the near future!