band

The band guard keeps an op’s output within a two-sided range around its simulated value. It adds two on-chain checks:

output ≥ simulated × (10000 − bps) / 10000, rounded down
output ≤ simulated × (10000 + bps) / 10000, rounded up

If the output at execution falls outside that range, the transaction reverts. The compile result reports no minimum for the guarded port.

When to use it

Use band where a move in either direction is a problem, above all the pool price a liquidity deposit sees. A deposit that executes after the price moved, for example after a sandwich trade, adds liquidity at a worse ratio, and a floor alone can’t catch that. The Uniswap deposit ops expose the price they read just before the deposit for this guard:

Op	Port	Value
`uniswapV2.addLiquidity`	`poolPrice`	The pair’s price, `reserve1 × 2^112 / reserve0`. Another user’s liquidity add leaves it unchanged; only a swap moves it.
`uniswapV3.mint`, `uniswapV3.increaseLiquidity`	`sqrtPriceX96`	The pool’s square-root price. A band of N bps on `sqrtPriceX96` allows about 2N bps of price movement, so halve the tolerance you want on the price.

These ops have no other price protection. Pair the band guard with a slippage guard on liquidity, which floors the LP amount the deposit mints.

Config

Field	Type	Description
`port`	string	The op’s output port to check: a `resource_output` or a `handle`.
`bps`	integer	Tolerance in basis points on each side of the simulated value. `50` is 0.5%.

Example

Add 1,000 USDC and 0.25 WETH to the Uniswap V2 USDC/WETH pair on Ethereum. The transaction reverts if the pool price moved more than 0.5% either way, or if the deposit mints less than 99.5% of the simulated LP amount:

import { createComposeSdk, guards, materialisers, resources } from '@lifi/composer-sdk';

// Ethereum mainnet
const USDC = '0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48';
const WETH = '0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2';
const UNISWAP_V2_ROUTER = '0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D';
const UNISWAP_V2_FACTORY = '0x5C69bEe701ef814a2B6a3EDD4B1652CB9cc5aA6f';
const USDC_WETH_PAIR = '0xB4e16d0168e52d35CaCD2c6185b44281Ec28C9Dc';

const sdk = createComposeSdk({
  baseUrl: 'https://composer.li.quest',
  apiKey: process.env.LIFI_API_KEY!,
});

const builder = sdk.flow(1, {
  name: 'uniswap-v2-add-liquidity',
  inputs: {
    usdcIn: resources.erc20(USDC, 1),
    wethIn: resources.erc20(WETH, 1),
  },
});

builder.uniswapV2.addLiquidity('add-liquidity', {
  bind: { tokenA: builder.inputs.usdcIn, tokenB: builder.inputs.wethIn },
  config: {
    router: UNISWAP_V2_ROUTER,
    factory: UNISWAP_V2_FACTORY,
    pair: USDC_WETH_PAIR,
  },
  guards: [
    // Revert unless the pool price read before the deposit is within ±0.5%
    // of the simulated price, in either direction.
    guards.band({ port: 'poolPrice', bps: 50 }),
    // Revert unless the deposit mints at least 99.5% of the simulated LP amount.
    guards.slippage({ port: 'liquidity', bps: 50 }),
  ],
});

await builder.compile({
  signer: '0xYourSignerAddress',
  inputs: {
    usdcIn: materialisers.directDeposit({ amount: '1000000000' }), // 1,000 USDC
    wethIn: materialisers.directDeposit({ amount: '250000000000000000' }), // 0.25 WETH
  },
  sweepTo: builder.context.sender,
  // The LP token has no price, so the default price-impact check would read
  // the deposit as a total loss. 0 skips it; the two guards are the protection.
  maxPriceImpactBps: 0,
});

The unused side of the deposit comes back as a residual and is swept to the sender with the LP tokens. For a full Uniswap walkthrough, including V3 positions, see Add liquidity on Uniswap.

Introduction

Integrate via Composer API

Integrate via LI.FI API

Resources

When to use it

Config

Example

​When to use it

​Config

​Example

When to use it

Config

Example