uniswap

Call exactInputSingle on SwapRouter02 (0x68b3465833fb72A70ecDF485E0e4C7bD8665Fc45) with tokenIn, tokenOut, fee tier, amountIn, and amountOutMinimum. Quote first with QuoterV2, then apply slippage tolerance to compute amountOutMinimum before executing.

V3 deploys one contract per pool via a factory, while V4 uses a singleton PoolManager holding all pools identified by a PoolKey (currency0, currency1, fee, tickSpacing, hooks). V4 also supports hook contracts that customize behavior at swap and liquidity lifecycle points.

Compute price as (sqrtPriceX96 / 2^96)^2, then adjust for token decimal differences by multiplying by 10^(decimals0 - decimals1). Always verify token ordering by reading pool.token0(), since the numerically smaller address is token0.

STF means the token transfer into the pool failed due to insufficient balance or missing approval. Approve the correct spender: SwapRouter02 for direct swaps, or Permit2 (0x000000000022D473030F116dDEE9F6B43aC78BA3) when using UniversalRouter, capped at uint160 max.

Hook addresses must encode enabled callback flags in their leading bits. Use HookMiner.find with CREATE2 to mine a salt producing an address matching your getHookPermissions flags, deploy the hook at that address, then initialize the pool referencing it.

Use 100 (0.01%) for stablecoin pairs, 500 (0.05%) for major pairs like WETH/USDC, 3000 (0.3%) for standard pairs, and 10000 (1%) for volatile or exotic tokens. Query the factory's getPool across all tiers to find where liquidity exists.