When Tokens Land in a Pool, Check Reserves Before Adding

A direct token transfer changes a pool’s balance, but its recorded reserve changes only when the pool updates it. In a reserve-based pool, that update can shift the quoted price without creating LP shares, the pool’s tokens that represent an ownership claim. Check whether the transfer is still unrecorded before adding your own funds.

• A donation does not automatically give its sender a share of the pool.
• After a reserve update, a one-sided donation can move the pool’s price.
• Before adding liquidity, check whether extra tokens are balances above recorded reserves.

What counts as a pool donation?

A donation is a token sent straight to a pool contract without using its normal liquidity-deposit process. The pool’s actual balance rises, but its recorded reserve—the amount the swap logic treats as available—may stay the same for now.

That gap matters in a reserve-based pool, such as a typical version-two automated market maker. An automated market maker, or AMM, sets swap prices from the amounts of tokens in its pool. A direct transfer can change what the contract holds before it changes the reserves used for pricing.

What changes when reserves update?

When the pool updates its reserves, it records the tokens it holds at that moment. In a version-two-style pool, a public sync function can do this; some other pool actions also update reserves. The exact mechanism depends on the pool’s contract version.

For example, imagine a pool with 100 Token A and 100 Token B, and someone sends it 10 extra A. Before the update, the recorded reserves may still be 100 and 100. After an update, they may read 110 A and 100 B, although the LP-share supply has not grown.

That reserve ratio can change the pool’s quoted price. In a simple constant-product pool, where the two reserve amounts multiply to set the trading curve, the example shifts the spot price from 1 B per A to about 0.91 B per A. Traders may then arbitrage—trade against a price gap—to bring it closer to other markets. Existing providers bear the resulting change in pool value.

Who gets tokens sent before an update?

A direct transfer does not mint shares for its sender. But in a version-two-style pool, an unrecorded donation can affect the next liquidity deposit: the contract may calculate new shares from the token balances above the recorded reserves. That means the next depositor could receive credit for some donated tokens.

This is the common mistake: seeing a larger token balance and assuming it already belongs to existing providers in proportion to their shares. If reserves have not updated, that assumption can be wrong. Check both the pool’s token balances and its recorded reserves on BaseScan, Base’s block explorer, before depositing.

If you’re adding liquidity on Base, BaseSwap is one way to work with pools; see BaseSwap liquidity pools for more on that task. First identify the pool’s contract version, because concentrated-liquidity pools—where funds are assigned to chosen price ranges—do not all follow this reserve-based example.

What should you check before adding liquidity?

Compare each token’s actual balance with its recorded reserve, and look for a recent transfer that may explain any gap. Then check whether a reserve update has happened since. BaseScan can show token transfers and contract transactions, but interpreting a particular pool still depends on its contract.

Use the current recorded ratio when deciding how much of each token to supply to a reserve-based pool. A deposit in the wrong ratio may leave one token unused or change the pool price. If you cannot confirm how that pool handles extra balances, wait for its records to update or verify the contract version before depositing.

Frequently asked questions

Does a donation earn fees for its sender?

No. A direct transfer does not itself mint LP shares, so it does not give the sender a proportional claim on future swap fees. If reserves update, the extra tokens become part of the pool’s recorded reserves and can affect trades. Who benefits from later deposits or trades depends on the pool’s contract rules and the timing of the update.

Can a donation change the pool’s price?

It can, if the donation is recorded as a reserve change in a reserve-based pool. Adding only one token changes the ratio used for the pool’s spot price. The size and direction depend on the added amount and starting reserves. Traders may arbitrage the new price against other markets, but that does not guarantee the pool returns to its earlier value.

Can the next depositor receive credit for a donation?

In a version-two-style pool, possibly. If the transfer raises actual balances but the reserves have not yet updated, the next mint calculation may count the excess as part of the deposited amounts. Once reserves have been updated, that excess is no longer unrecorded. Other pool designs can handle donations differently, so check the specific contract.

How can I tell if a pool is version two style?

Check the pool contract address and its verified code or documentation, rather than relying only on the exchange name. On Base, BaseScan can help you find the contract and inspect its transactions. Look for reserve-based functions and how liquidity shares are minted. If you cannot establish the design, do not assume this donation example applies.

Takeaway: check recorded reserves and pool version before adding funds.