> ## Documentation Index
> Fetch the complete documentation index at: https://anypay-edge.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# ERC-20 Helpers

> Token registry, calldata builders, and slippage helper for composing actions

Side-effect-free helpers for building ERC-20 calls and looking up tokens. Pair them with [`custom`](/sdk/composable-actions/building-actions#custom-arbitrary-contract-call-escape-hatch) for ergonomic custom calldata.

```ts theme={null}
import { parseUnits } from 'viem'
import {
  erc20Utils,
  buildCall,
  buildApproveAndCall,
  buildErc20Approve,
  getAmountWithSlippage,
} from '0xtrails'
```

## Token registry — `erc20Utils`

Look up canonical token metadata (address + decimals) per chain.

```ts theme={null}
erc20Utils.USDC.onChain('base')
// → { address: "0x833…", decimals: 6, name: "USD Coin", imageUrl: "…" }

erc20Utils.USDC.addressOn('base')
erc20Utils.USDC.decimalsOn('base')
```

### Generic symbol lookup

For symbols not pinned as top-level properties:

```ts theme={null}
erc20Utils.token('WETH').onChain(42161)
```

### ERC-20 calldata builders

Standard calls, amounts are raw `bigint` wei:

```ts theme={null}
const amount = parseUnits('1', 6) // 1 USDC

erc20Utils.approve({ tokenAddress, spender, amount })
erc20Utils.transfer({ tokenAddress, to, amount })
erc20Utils.transferFrom({ tokenAddress, from, to, amount })
```

Each returns a `Call`. To include one in an action list, spread it into `custom({ ...call })`:

```ts theme={null}
import { custom, erc20Utils } from '0xtrails'
import { parseUnits } from 'viem'

custom({
  ...erc20Utils.approve({
    tokenAddress: erc20Utils.USDC.addressOn('base'),
    spender: '0xMyContract…',
    amount: parseUnits('100', 6),
  }),
})
```

## Composing calls — `buildCall` / `buildApproveAndCall`

`buildCall` constructs a `Call` from an ABI + function name + args:

```ts theme={null}
import { buildCall } from '0xtrails'

const stake = buildCall({
  to: STAKING_CONTRACT,
  data: {
    abi: stakingAbi,
    functionName: 'stake',
    args: [parseUnits('100', 6)],
  },
})
```

`buildApproveAndCall` bundles an approval **and** a follow-up call into a `[approve, call]` tuple:

```ts theme={null}
import { buildApproveAndCall, erc20Utils } from '0xtrails'

const [approve, stakeCall] = buildApproveAndCall({
  token: erc20Utils.USDC.addressOn('base'),
  call: stake,
  // amount defaults to maxUint256
})
```

## Slippage helper — `getAmountWithSlippage`

Subtracts `bps` basis points (1 bp = 0.01%) from a raw `bigint` amount.

```ts theme={null}
getAmountWithSlippage(parseUnits('1', 6), 50) // 1 USDC, 0.5% → 0.995 USDC
getAmountWithSlippage(parseUnits('1', 6), 500) // 1 USDC, 5%  → 0.95 USDC
```

Handy for computing a safe `minAmountOut` or `amountOutMinimum` before handing it to [`swap`](/sdk/composable-actions/building-actions#swap-on-chain-token-swap) or the [chain-scoped Uniswap V3 / SushiSwap V3 adapters](/sdk/composable-actions/building-actions#swap-utilities).