# Unbalanced Add Via Swap Router API

The Unbalanced Add Via Swap Router can be used to interact with Balancer onchain via state changing operations or used to query operations in an off-chain context.

Specialized router for adding unbalanced liquidity to two-token pools by combining a proportional add with a swap.

Use Case: You want to add liquidity with an exact amount of one token and an approximate amount of another, but regular unbalanced adds might be inefficient or unavailable.

# State-changing functions

# addLiquidityUnbalanced

function addLiquidityUnbalanced(
    address pool,
    uint256 deadline,
    bool wethIsEth,
    AddLiquidityAndSwapParams calldata params
) external payable returns (uint256[] memory amountsIn);

Adds liquidity to a two-token pool with one exact amount and one adjustable amount by combining a proportional add with a swap in the same transaction.

How it works:

1. Performs a proportional add with calculated amounts
2. Swaps the difference in the pool to achieve the exact desired amount
3. Results in exact exactAmount of exactToken and up to maxAdjustableAmount of the other token

Restrictions:

• Only works with two-token pools
• Final exactToken amount must exactly match exactAmount
• Final other token amount must not exceed maxAdjustableAmount

Parameters:

Returns:

# Queries

# queryAddLiquidityUnbalanced

function queryAddLiquidityUnbalanced(
    address pool,
    address sender,
    AddLiquidityAndSwapParams calldata params
) external returns (uint256[] memory amountsIn);

Queries an addUnbalancedLiquidityViaSwap operation without actually executing it.

Parameters:

Returns:

# Data Structures

# AddLiquidityAndSwapParams

struct AddLiquidityAndSwapParams {
    uint256 exactBptAmountOut;      // Exact BPT to receive
    IERC20 exactToken;              // Token with exact amount
    uint256 exactAmount;            // Exact amount of exactToken
    uint256 maxAdjustableAmount;    // Max amount of other token
    bytes addLiquidityUserData;     // Data for add operation
    bytes swapUserData;             // Data for swap operation
}

Parameters for adding liquidity via a combination of proportional add and swap.

Fields: