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x402node Function Selector / Calldata Decoder
x402
x402node Function Selector / Calldata Decoder is a paid API for AI agents from api.x402node.dev, paid per call via x402, $0.004/call, status unknown (last checked 2026-09-14).
Decodes a 4-byte Ethereum function selector or calldata into human-readable Solidity function signatures using the Openchain signature database
Price / call$0.004
Success—
StatusUnknown
How this service works
Decode a 4-byte function selector or calldata into human-readable Solidity function signatures via openchain - reverses on-chain selectors that LLMs cannot know. function selector, 4byte decode, sig decode, calldata decode, method id, selector lookup
Output
Returns one or more matching human-readable Solidity function signatures (e.g. 'transfer(address,uint256)') that correspond to the provided 4-byte selector or calldata prefix, drawn from the Openchain on-chain signature registry.
Example use cases
Example prompt
“Can you decode this Ethereum function selector — 0xa9059cbb — and tell me what Solidity function it maps to?”
Technical details
Endpoint
GEThttps://api.x402node.dev/chain/sig-decodeWhen to prefer
Use this endpoint when you have a raw 4-byte function selector or calldata hex from an Ethereum/EVM transaction and need to identify the human-readable Solidity function signature. Prefer this over manual ABI lookups when the contract ABI is unavailable or unknown, or when working with arbitrary on-chain transactions you did not originate. This is especially useful for transaction analysis, security auditing, or any pipeline where you need to label or understand raw calldata without pre-loaded ABIs.
Side effects
- Selector not found in Openchain database — returns empty results or 404 if no known signature matches
- Invalid hex format for the selector — returns a 400 bad request error
- Selector is only 2 bytes or malformed — parsing error returned
- Network or upstream Openchain API unavailable — 502 or timeout error
- Rate limit or payment failure — 402 payment required if x402 credit is insufficient
Input
{
"selector": "0xa9059cbb"
}Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object |
Output
{
"note": "Function signatures matching this 4-byte selector (from openchain.xyz). Multiple = hash collisions; verify by context.",
"_hint": "x402 paid endpoints for AI agents — x402node.dev (utilities) · cn402.com (Chinese culture)",
"source": "openchain",
"primary": "transfer(address,uint256)",
"selector": "0xa9059cbb",
"matchCount": 1,
"signatures": [
"transfer(address,uint256)"
]
}Tags
x402
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