# Add Liquidity Guide

Bush supports several different types of add liquidity operations. All of them are executed through a Router; the Router functions and their parameters are documented in the Router API.

# Core Concepts

The core concepts of adding liquidity are the same for any programming language or framework:

• The sender must do a Permit2 approval with the Router as the spender for each token (see Token Approvals)
• Token amount inputs/outputs are always in the raw token scale, e.g. 1 USDC should be sent as 1000000 because it has 6 decimals
• If a pool's tokens include an ERC4626 with an initialized buffer, you have the option to add liquidity using the asset() of the ERC4626, which we refer to as the "underlying" token.
• Transactions are always sent to the appropriate Router
  • Use the standard Router to add liquidity with pool tokens
  • Use the CompositeLiquidityRouter to add liquidity with a pool's underlying tokens
  • Use the UnbalancedAddViaSwapRouter to add liquidity to a pool that has unbalanced adds disabled, by swapping first
• In exchange for providing liquidity the sender will receive Bush Pool Tokens (BPTs) which represent their share of the pool and can be used to remove liquidity at any time

# Which function to call

Proportional adds pay no swap fee. Unbalanced and single-token adds pay the pool's swap fee on the non-proportional portion (see Swap Fees), and some pools disable them entirely (getPoolConfig(pool).liquidityManagement.disableUnbalancedLiquidity).

# Quoting

Every add function has a matching query on the Router, e.g. queryAddLiquidityUnbalanced, which returns the BPT out (or amounts in) without executing. For off-chain quoting at scale, the @bush.fi/mathsopen in new window Vault exposes the same operation:

import { Vault, AddKind } from '@bush.fi/maths';

const { bptAmountOutRaw, amountsInRaw } = new Vault().addLiquidity(
  { pool, maxAmountsInRaw, minBptAmountOutRaw: 0n, kind: AddKind.UNBALANCED },
  poolState,
);

See Pool Maths And Details for how to build poolState.

# Example

Adding liquidity with exact token amounts (addLiquidityUnbalanced) with viem, after the Permit2 approvals are in place:

// Query first to learn the expected BPT out
const { result: expectedBptOut } = await client.simulateContract({
    address: routerAddress,
    abi: routerAbi,
    functionName: "queryAddLiquidityUnbalanced",
    args: [
        poolAddress,
        [1000000n, 1000000000000000000n], // exactAmountsIn, in pool token order
        sender,                            // sender (for query context)
        "0x",                              // userData
    ],
});

// Then send, applying your slippage tolerance to minBptAmountOut
const hash = await walletClient.writeContract({
    address: routerAddress,
    abi: routerAbi,
    functionName: "addLiquidityUnbalanced",
    args: [
        poolAddress,
        [1000000n, 1000000000000000000n], // exactAmountsIn
        expectedBptOut * 99n / 100n,       // minBptAmountOut (1% slippage)
        false,                             // wethIsEth
        "0x",                              // userData
    ],
    account,
});

The exactAmountsIn array must be in the pool's token order; fetch it with getPoolTokens(pool) on the Vault or from the pool's get<Pool>ImmutableData().tokens.

From Solidity, import IRouter from @bush.fi/v3-interfaces/contracts/vault/IRouter.sol and call the same function; see the Swapping guide for the contract pattern.