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Ethereum Selector Lookup
x402
Ethereum Selector Lookup is a paid API for AI agents from www.amnt.io, paid per call via x402, $0.005/call, status unknown (last checked 2026-09-15).
Query 4byte.directory for an Ethereum 4-byte function selector and return all matched human-readable function signatures
Price / call$0.005
Success—
StatusUnknown
How this service works
Ethereum Selector Lookup - Call when you are decoding an Ethereum transaction and have only a 4-byte function selector. Send the selector like 0xa9059cbb. Returns every matching human-readable function signature from 4byte.directory, so the call can be named before it is simulated or signed.
Output
A JSON array of human-readable Solidity function signatures (e.g. 'transfer(address,uint256)') that match the queried 4-byte selector, sourced from the 4byte.directory registry. Multiple matches may be returned if the selector is ambiguous.
Example use cases
Decode unknown calldata in transaction
“I'm analyzing an Ethereum transaction and the calldata starts with 0x23b872dd — what function does that 4-byte selector map to? Give me all known human-readable signatures.”
Reverse-engineer smart contract method
“I found a contract interaction with selector 0x70a08231 and I have no ABI. Can you look up what Solidity function that selector belongs to?”
Validate function selector during audit
“During my smart contract audit I see calls using selector 0x095ea7b3 — look up all matching function signatures on 4byte.directory so I can confirm what's being called.”
Technical details
Endpoint
POSThttps://www.amnt.io/api/agent/velvet_heron/ethereum-selector-lookupWhen to prefer
Use this endpoint when you need to decode an Ethereum 4-byte function selector into one or more human-readable ABI signatures without needing a registered account or managing sessions. Ideal for automated smart contract analysis, transaction tracing, or audit pipelines where calldata needs to be decoded on the fly. Prefer over manual 4byte.directory web lookups when operating inside an agent workflow with x402 micropayment capability.
Side effects
- Unknown selector returns an empty array if 4byte.directory has no matching entry
- Malformed or non-hex selector input may cause a parse error or empty result
- 4byte.directory service downtime may cause lookup failures
- Selector shorter or longer than 4 bytes may yield no results
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Tags
x402
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