npx skills add ...
npx skills add affaan-m/ecc --skill evm-token-decimals
Prevent silent decimal mismatch bugs across EVM chains. Covers runtime decimal lookup, chain-aware caching, bridged-token precision drift, and safe normalization for bots, dashboards, and DeFi tools. Use when handling token amounts across EVM chains, or when a balance, price, or transfer amount is off by orders of magnitude.
npx skills add affaan-m/ecc --skill evm-token-decimals
Silent decimal mismatches are one of the easiest ways to ship balances or USD values that are off by orders of magnitude without throwing an error.
Never assume stablecoins use the same decimals everywhere. Query decimals() at runtime, cache by (chain_id, token_address), and use decimal-safe math for value calculations.
Do not hardcode 1_000_000 because a symbol usually has 6 decimals somewhere else.
Log the fallback and keep it visible. Old or non-standard tokens still exist.
decimals() at runtimeDecimal, BigInt, or equivalent exact math, not floatfrom functools import lru_cache
@lru_cache(maxsize=512)
def get_decimals(chain_id: int, token_address: str) -> int:
w3 = get_web3_for_chain(chain_id)
contract = w3.eth.contract(
address=Web3.to_checksum_address(token_address),
abi=ERC20_ABI,
)
return contract.functions.decimals().call()try:
decimals = contract.functions.decimals().call()
except Exception:
logging.warning(
"decimals() reverted on %s (chain %s), defaulting to 18",
token_address,
chain_id,
)
decimals = 18interface IERC20Metadata {
function decimals() external view returns (uint8);
}
function normalizeToWad(address token, uint256 amount) internal view returns (uint256) {
uint8 d = IERC20Metadata(token).decimals();
if (d == 18) return amount;
if (d < 18) return amount * 10 ** (18 - d);
return amount / 10 ** (d - 18);
}import { Contract, formatUnits } from 'ethers';
const ERC20_ABI = [
'function decimals() view returns (uint8)',
'function balanceOf(address) view returns (uint256)',
];
async function getBalance(provider: any, tokenAddress: string, wallet: string): Promise<string> {
const token = new Contract(tokenAddress, ERC20_ABI, provider);
const [decimals, raw] = await Promise.all([
token.decimals(),
token.balanceOf(wallet),
]);
return formatUnits(raw, decimals);
}cast call <token_address> "decimals()(uint8)" --rpc-url <rpc>