NFT balance, Base. How many NFTs of one ERC-721 collection a wallet holds on Base (balanceOf), with the collection's name and symbol. Use to check a holder before a token-gated action or to see whether a wallet still holds a collection; for who holds one token id use base_nft_owner. Both inputs are 0x addresses; a missing contract is 404, a contract that is not ERC-721 422, both uncharged.

SWIFT code, BIC validation. Check a BIC (SWIFT code) against the ISO 9362 structure: institution code, a real country code with its name, location code, branch code, whether it is the head office (XXX or 8 characters), a test BIC or a passive participant, and the 11-character form. Computed locally; it checks the format and country, not whether the bank exists. Use before an international transfer or to clean payment data; for account numbers use validate_iban.

Base ERC-20 token info. Look up the name, symbol, decimals and total supply of an ERC-20 token contract on Base, live from the contract. Use to identify an unknown token address or to format raw amounts; for a holder's balance use base_token_balance. Input is a ticker (USDC, WETH…) or the token's 0x contract address; an address that is not an ERC-20 contract returns 422, uncharged.

NFT metadata, Ethereum. NFT metadata on Ethereum: the token URI of one ERC-721 token id (tokenURI) and the JSON it points to (name, description, image, attributes), read from data: URIs, https or ipfs:// (through ipfs.io). Strings over 1,000 characters, such as on-chain SVG images, are shortened. Use to show or check what an NFT is; for its owner use eth_nft_owner. A token that does not exist is 422, uncharged; unreachable metadata is reported in metadataError.

Ethereum contract check. Check whether a 0x address on Ethereum is a smart contract or a plain wallet: bytecode size, and whether it is an EIP-1167 minimal proxy and which implementation it points to. Use before sending funds or approving a spender; for a fuller risk verdict use check_counterparty. A malformed address is rejected with 400, uncharged.

Gas history, Ethereum gas price. Gas price history on Ethereum (eth_feeHistory): base fee in gwei for each of the last N blocks (5-100, default 20), how full each block was, and the 10th, 50th and 90th percentile priority fees, with the low, average and high base fee over the window. Use to judge whether fees are rising, pick a priority fee or time a transaction; for the current price alone use eth_gas.

NFT balance, Ethereum. How many NFTs of one ERC-721 collection a wallet holds on Ethereum (balanceOf), with the collection's name and symbol. Use to check a holder before a token-gated action or to see whether a wallet still holds a collection; for who holds one token id use eth_nft_owner. Both inputs are 0x addresses; a missing contract is 404, a contract that is not ERC-721 422, both uncharged.

Ethereum account nonce. Read the transaction count (nonce) of a 0x address on Ethereum, both confirmed and including pending transactions. Use to build the next transaction or to tell whether an address has ever sent anything; for its balance use eth_balance. A malformed address is rejected with 400, uncharged.

Ethereum recent event logs. Recent contract event logs on Ethereum (eth_getLogs): the events a contract emitted over the last N blocks (1-1,000, default 50), optionally filtered by topic0 (the 0x 32-byte event signature hash). Returns up to 100 logs with block, transaction hash and topics. Use to watch transfers or contract events; for one transaction's outcome use eth_receipt.

Proxy implementation, Ethereum. Find the implementation behind a proxy contract on Ethereum: reads the EIP-1967 implementation, beacon and admin slots, EIP-1822 (UUPS), the older OpenZeppelin layout and EIP-1167 minimal-proxy bytecode, and names the kind found. Use before trusting or decoding a contract whose code can be swapped by its admin; for a fuller risk verdict use contract_risk. A malformed address is 400; an address without code is 404, both uncharged.

NFT owner, Ethereum. Owner of an NFT on Ethereum: the wallet that holds one ERC-721 token id right now (ownerOf), plus the collection's name and symbol. Use to verify who holds an NFT before a trade, a mint gate or an airdrop; for how many a wallet holds use eth_nft_balance, for the token's metadata eth_nft_metadata. A missing contract is 404, a token that does not exist 422, both uncharged.

Ethereum transaction receipt. Transaction receipt on Ethereum (eth_getTransactionReceipt): success or reverted, gas used, effective gas price, fee paid in ETH, number of event logs and any contract created. Use to confirm a payment or call went through; for sender, value and calldata use eth_tx. Input is a 0x-prefixed 64-hex hash; a pending or unknown hash returns 404, uncharged.

Ethereum transaction. Look up an Ethereum transaction by hash: sender, recipient, value in ETH, nonce, gas limit, the 4-byte function selector and its block. Use to see what was sent or whether it exists; for success or failure and fees paid use eth_receipt, for emitted events eth_logs. Input is a 0x-prefixed 64-hex hash; an unknown hash returns 404, uncharged.

Storage slot read, Ethereum. Read one raw storage slot of a contract on Ethereum (eth_getStorageAt): the 32-byte word, as a number and, when it holds one, as an address. Slot is a decimal index or a 0x 32-byte key (mapping and proxy slots). Use to inspect contract state that has no getter, owners or implementation pointers; for proxies use eth_proxy. A malformed address or slot is rejected with 400, uncharged.

Ethereum ERC-20 balance. ERC-20 token balance of a wallet on Ethereum (USDC, USDT, WETH or any token, via balanceOf): raw amount, decimals, symbol and the human-readable amount, live from the token contract. Use to check stablecoin or token holdings before a transfer or trade; for the native coin use eth_balance. Both inputs are 0x addresses (40 hex characters); no contract returns 404 and a non-ERC-20 contract 422, both uncharged.

Ethereum ERC-20 token info. Look up the name, symbol, decimals and total supply of an ERC-20 token contract on Ethereum, live from the contract. Use to identify an unknown token address or to format raw amounts; for a holder's balance use eth_token_balance. Input is a ticker (USDC, WETH…) or the token's 0x contract address; an address that is not an ERC-20 contract returns 422, uncharged.

HMAC signature. Compute an HMAC of a message with a key using SHA-256 (default), SHA-1, SHA-384 or SHA-512, in hex and base64. Use to check webhook signatures. The key is used only for this call and is not stored.

Optimism contract check. Check whether a 0x address on Optimism is a smart contract or a plain wallet: bytecode size, and whether it is an EIP-1167 minimal proxy and which implementation it points to. Use before sending funds or approving a spender; for a fuller risk verdict use check_counterparty. A malformed address is rejected with 400, uncharged.

Gas history, Optimism gas price. Gas price history on Optimism (eth_feeHistory): base fee in gwei for each of the last N blocks (5-100, default 20), how full each block was, and the 10th, 50th and 90th percentile priority fees, with the low, average and high base fee over the window. Use to judge whether fees are rising, pick a priority fee or time a transaction; for the current price alone use op_gas.

Optimism gas price. Current gas price on Optimism (eth_gasPrice): gas price, base fee and suggested priority fee in gwei, plus what a plain ETH transfer (21,000 gas) costs right now. Takes no input. Use before sending a transaction or to decide whether to wait; for the fee a past transaction actually paid use op_receipt.