Single-sided liquidity deposits: why adding one token can have a cost

Compare identical starting value

Suppose an equal-value two-asset pool is balanced. Adding 50 valuation units of A and 50 of B preserves that proportion. Adding 100 of A changes it. A single-action interface can handle the second case, but the resulting LP claim is priced by the pool’s rules rather than by treating both deposits as identical.

An exact LP-token-output instruction can require a variable input amount, while an exact input instruction can produce variable LP output. The labels on the quote matter.

Read the minimum share output

Inspect how many pool tokens will be minted and which fees are included. A one-token exit has the reverse distinction: receiving only one asset can differ economically from receiving the proportional basket and retaining it.

Do not assume an integration called single-sided always uses Balancer’s mechanism. A wrapper may perform an external swap before joining.

The receipt determines subsequent exposure

After the join, the holder owns a pool claim whose composition changes with trading. Starting with only A does not mean the claim will forever be redeemable for the original number of A tokens. A donation action is more different still: it adds value without minting an ownership receipt.