# Ethereum Calldata Decoder & Keccak256 Selector

> 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.

## Facts

- Endpoint: POST https://api.24klabs.ai/api/eth-calldata-decode
- Price: $0.002/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-13
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/ethereum-calldata-decoder-keccak256-selector-ba9d009a
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_aMOTj1f6NpzPjmFx-OHPH

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability ethereum-calldata-decoder-keccak256-selector-ba9d009a -d '<json body>'
```

Example prompt: Can you compute the keccak256 hash and 4-byte selector for the Solidity signature 'transfer(address,uint256)', and also decode the raw calldata '0xa9059cbb000000000000000000000000ab5801a7d398351b8be11c439e05c5b3259aec9000000000000000000000000000000000000000000000000002386f26fc10000' using types ['address','uint256']?

## When to prefer this

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.

## Known failure modes

- 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

## 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.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "signature": {
   "type": "string"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "selector": "0xa9059cbb"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/ethereum-calldata-decoder-keccak256-selector-ba9d009a/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.24klabs.ai](https://www.zero.xyz/host/api.24klabs.ai/llms.txt)