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Ethereum Calldata Decoder & Keccak256 Selector
x402
Ethereum Calldata Decoder & Keccak256 Selector is a paid API for AI agents from api.24klabs.ai, paid per call via x402, $0.002/call, status unknown (last checked 2026-09-13).
Computes the keccak256 hash and 4-byte function selector of a Solidity signature string, and optionally ABI-decodes raw hex calldata given an ordered list of static Solidity types.
Price / call$0.002
Success—
StatusUnknown
How this service works
Compute the keccak256 hash and 4-byte function selector of a signature string, and optionally ABI-decode raw hex calldata given an ordered list of static Solidity types.
Output
Returns the keccak256 hash of the provided signature string, the first 4 bytes of that hash as the function selector (hex), and if calldata and ABI types are provided, an ordered array of decoded parameter values corresponding to the supplied Solidity types.
Example use cases
Verify ERC-20 function selector
“What is the 4-byte function selector and keccak256 hash for the Solidity signature 'transfer(address,uint256)'? I want to confirm it matches 0xa9059cbb.”
Decode smart contract transaction input
“Decode this raw calldata hex '0xa9059cbb000000000000000000000000d8da6bf26964af9d7eed9e03e53415d37aa96045000000000000000000000000000000000000000000000000016345785d8a0000' using ABI types ['address','uint256'] so I can see the actual recipient address and token amount.”
Debug unknown contract call
“I have raw calldata '0x23b872dd000000000000000000000000abc...000000000000000000000000def...0000000000000000000000000000000000000000000000000de0b6b3a7640000' from a transaction — can you decode it with types ['address','address','uint256'] and also give me the keccak256 of 'transferFrom(address,address,uint256)'?”
Technical details
Endpoint
POSThttps://api.24klabs.ai/api/eth-calldata-decodeWhen to prefer
Use this endpoint when you need to compute Ethereum function selectors or keccak256 hashes from Solidity signatures without running a local Ethereum toolchain, or when you need to ABI-decode raw hex calldata from blockchain transactions using a known type list. Prefer this over general-purpose hashing endpoints because it is specifically designed for Solidity ABI encoding semantics and returns both the full hash and the canonical 4-byte selector in one call.
Side effects
- Invalid Solidity type in ABI list returns a type parsing error
- Malformed or truncated hex calldata causes decoding failure
- Calldata length mismatch with provided ABI types results in an error
- Missing required signature field returns a validation error
- Non-hex characters in calldata string cause parsing failure
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| signature | string |
Output
Schema · Response
{
"type": "json",
"example": {
"selector": "0xa9059cbb"
}
}Tags
x402
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