uniswap-swap-simulation - SKILL.md Agent Skill

name: uniswap-swap-simulation

description: Simulate and analyze Uniswap swaps including price impact, slippage, optimal routing, and gas estimation. Use when the user asks about swap execution, routing, price impact, or MEV considerations.

Uniswap Swap Simulation

Overview

This skill covers simulating Uniswap swaps, calculating price impact, and analyzing routing decisions.

Key Concepts

Price Impact: The change in pool price caused by a swap. Larger swaps have higher impact.
Slippage: Difference between expected and executed price, including price movement between submission and execution.
Routing: Finding the optimal path across pools and protocols for best execution.

Simulating a Swap

Use the Quoter contract to simulate swaps without executing:


import { createPublicClient, http, encodeFunctionData } from "viem";



// QuoterV2 for v3 pools

const quote = await client.readContract({

  address: quoterV2Address,

  abi: quoterV2Abi,

  functionName: "quoteExactInputSingle",

  args: [

    {

      tokenIn,

      tokenOut,

      amountIn,

      fee,

      sqrtPriceLimitX96: 0n,

    },

  ],

});



// Returns: [amountOut, sqrtPriceX96After, initializedTicksCrossed, gasEstimate]

Price Impact Calculation


function calculatePriceImpact(

  amountIn: bigint,

  amountOut: bigint,

  marketPrice: number, // token1/token0

  decimals0: number,

  decimals1: number,

): number {

  const executionPrice =

    Number(amountOut) / 10 ** decimals1 / (Number(amountIn) / 10 ** decimals0);

  return Math.abs(1 - executionPrice / marketPrice);

}

Slippage Tolerance

Stablecoin pairs: 0.01% - 0.05%
Major pairs (ETH/USDC): 0.1% - 0.5%
Volatile pairs: 0.5% - 1.0%
Low liquidity: 1% - 5%

Calculate minimum amount out:


const minAmountOut = (amountOut * (10000n - BigInt(slippageBps))) / 10000n;

Multi-hop Routing

For tokens without direct pools, route through intermediary tokens:


// ETH -> USDC -> DAI (two hops)

const path = encodePacked(

  ["address", "uint24", "address", "uint24", "address"],

  [WETH, 3000, USDC, 100, DAI],

);



const quote = await client.readContract({

  address: quoterV2Address,

  abi: quoterV2Abi,

  functionName: "quoteExactInput",

  args: [path, amountIn],

});

Gas Estimation

Typical gas costs by swap complexity:

Single hop: ~130,000 gas
Two hops: ~200,000 gas
Three hops: ~270,000 gas

Always add a 15-20% buffer to gas estimates.

MEV Considerations

When building swap tools:

Recommend private RPCs (Flashbots Protect) for large swaps
Warn users about sandwich attack risk for high-impact swaps
Suggest using deadline parameters to limit exposure