Docs — Kardly

The unit of account

A unit of account is whatever a market measures value in. Every exchange has one, and it shapes everything built on top of it. When the unit is dollars, every trade needs a cash leg: someone has to sell before anyone can buy.

When the unit is the collectible itself, that requirement disappears. A card is quoted in other cards. A Charizard is not worth a number; it is worth a Messi rookie plus a remainder, or a Pikachu straight across, or three smaller cards bundled together — whatever the book will actually give for it.

What this changes

Cash becomes optional. It settles the difference between two sides. It is no longer the medium of the trade.
Inventory becomes purchasing power. A collection that was previously illiquid is a set of standing bids.
Value is expressed in what you want. The quote arrives in the form you were going to convert into anyway.

What a bid is

A bid is an offer to acquire a specific card, denominated in cards. It names exactly what is being put up. Because collectibles are not fungible, the ask side is equally specific: a set, a print run, a grade, a slab — the exact object, not a category average.

Shapes a bid can take

Single card. One for one, straight across.
A stack. Several smaller cards bundled until they clear the ask.
Card plus cash. A card carries most of the trade; cash covers the remainder.
Counter-bid. The holder answers back by naming the cards they would take instead.

Any card in a collection can appear in any number of bids. Until one is accepted, a card is simply advertised in several directions at once — the way a cash balance can be bid into several markets.

The spread

Two cards rarely line up perfectly. The gap between what is asked and what is bid is the spread, and it has to be closed for a trade to happen.

Close it with another card. Add to the stack until the two sides agree.
Close it with cash. Cash appears here as a remainder, the smallest part of the trade rather than the point of it.
Leave it open. The bid stands. Someone else may take it, or the holder may counter.

Because the spread is negotiated in the same terms as the bid, agreement is reached over objects rather than over a price feed.

Matching

In a cash order book, matching is trivial: bids and asks are ordered by price, and the top of each side clears. In a collectible-denominated book, ranking is not one-dimensional. Two bids can be close in value and completely different in kind.

What a holder weighs

Composition. One card or several. A bundle is worth less to someone who only wants a single slot filled.
Direction. Whether the bid moves the collection toward what the holder is actually building.
Cash remainder. How much of the trade settles outside the book.
Condition and grade. The same card at two grades is two different assets.

So the book presents the offers rather than collapsing them into a single best price. Ranking is left where it belongs: with the person deciding what to part with.

Settlement

Once a bid is accepted, both sides owe a physical object. A card-denominated trade has two deliveries instead of one, which is exactly why settlement matters more here than in a cash market.

The card is the card. Identity, grade and slab match what the bid described.
Neither side delivers first. A swap where one party ships into the dark is not a market, it is trust.
The remainder moves with the cards. The spread settles as part of the same trade, not as a side arrangement.
A failed leg unwinds cleanly. If one side does not deliver, the other gets their card back.

Graded and slabbed cards make this tractable: the grader has already answered the identity question, so the book can quote the slab rather than a photograph.

The network

Kardly runs on Robinhood Chain mainnet, and only there. There is no testnet deployment, no second network to pick from, and no path that quietly falls back to another chain.

Chain ID 4663. Read from the network itself and checked against 4663, rather than assumed.
An Arbitrum Orbit layer 2 with full EVM compatibility, so ordinary Ethereum tooling works.
ETH is the native currency. Cash added to close a spread moves as WETH, because a signed bid has to be pullable when the other side settles.

How that is enforced

The exchange cannot be deployed anywhere else. Its constructor reverts unless the chain id is 4663, and every function that changes state checks again at call time.
A signature cannot travel. The chain id is part of the EIP-712 domain, so a bid signed for 4663 is meaningless on any other chain.
The site will not sign off-network. Signing is disabled unless the wallet is on 4663, and the chain is re-checked with the wallet at the moment of signing rather than trusted from earlier.

Why card to card

The dollar loop imposes a cost that has nothing to do with the cards. To move from one collectible to another, a collector currently has to list, wait for a buyer, ship, receive cash, hunt for the next card, and hope it is still available at a price they accept. Each step is a place the trade can die.

Card to card removes the middle entirely. The two things a collector cares about — what leaves the collection and what enters it — are decided in a single move.

The second-order effect

Once cards can bid on cards, a collection stops being a static shelf. Every card in it is simultaneously an asset and a live offer for something else. The binder becomes buying power without anything being sold.

Terms

Order book: The standing offers on both sides of a market. Here the rows are cards rather than prices.
Unit of account: What a market measures value in. Here it is the collectible itself.
Ask: The specific card someone holds and is willing to part with.
Bid: An offer to acquire that card, made of one or more cards, optionally plus cash.
Spread: The gap between what is asked and what is bid, closed with cards or with a cash remainder.
Stack: Several cards bundled into a single bid.
Counter-bid: The holder's reply naming what they would actually accept.
Cash leg: The sell-for-cash step a dollar-denominated market requires before any purchase.

Questions

Is this just trading?

Trading is a private negotiation between two people. An order book is public, standing and competitive: bids sit against a card whether or not the holder is currently talking to anyone, and they compete with each other. That is the difference between a swap and a market.

Does cash disappear entirely?

No. Cash stays available to close a spread. What changes is its role: it settles the remainder instead of denominating the trade.

How are two different cards compared?

They are not reduced to a single number by the book. Bids are shown as they were made and the holder decides which they prefer. Dollar references remain useful as a sanity check; they are not the unit the trade is written in.

What about ungraded cards?

Grading is what lets a book quote an object instead of a photograph. Ungraded cards are harder to denominate precisely, because condition is the disputed part of the trade rather than a settled fact.

Why would a holder take cards instead of cash?

Because most collectors were going to convert the cash into cards anyway. Taking cards directly skips the conversion, the waiting, and the risk that the card they wanted is gone by the time the money arrives.

The model