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ABI Function/Event Selector Generator
x402
ABI Function/Event Selector Generator is a paid API for AI agents from x402-audit.tatschluizguilherme.workers.dev, paid per call via x402, $0.1/call, status unknown (last checked 2026-09-15).
Computes the 4-byte function selector or 32-byte event topic0 from a human-readable Solidity signature using Keccak-256, with no RPC or API key required.
Price / call$0.1
Success—
StatusUnknown
How this service works
Pay-per-call on-chain API for AI agents and developers: wallet audits, token safety audits (honeypot detection), live gas prices, token prices, transaction receipts, balances, ENS resolution, block data, ERC-20 allowances, transaction simulation, swap quotes and multicall batches — all computed on-chain via public RPCs (no external market API). Pay per request in USDC on Base via the x402 exact scheme (EIP-3009 transferWithAuthorization). No API key, no signup, no subscription.
Output
Returns the 4-byte function selector (hex) or 32-byte event topic0 hash, along with the full keccak256 of the canonical signature, parsed input types, and a verification flag indicating whether the selector appears in the known /decode dictionary.
Example use cases
ERC-20 function selector lookup
“Give me the 4-byte ABI selector for the ERC-20 approve function — the signature is approve(address,uint256) — and confirm it matches the known dictionary.”
Event topic0 for Transfer event
“I need the 32-byte topic0 hash for the ERC-20 Transfer event, signature Transfer(address,address,uint256), using kind=event.”
Selector for complex tuple function
“Compute the function selector for a Solidity function with a tuple parameter: execute(address,(bytes,address,uint256,uint256),uint256) — I need the 4-byte selector and the full keccak256.”
Technical details
Endpoint
GEThttps://x402-audit.tatschluizguilherme.workers.dev/selectorWhen to prefer
Choose this endpoint when you need to compute Solidity function selectors or event topic0 hashes offline, without any RPC connection, blockchain node, or Etherscan API key. Ideal for agent workflows that need instant, deterministic ABI encoding — especially when building calldata, filtering event logs, or verifying function IDs in a chain-agnostic way.
Side effects
- Malformed or invalid function signature returns a parse error
- Unsupported parameter syntax (e.g. nested tuples beyond spec) may cause incorrect output
- Missing kind field defaults to function selector; forgetting kind=event returns wrong hash length for events
- Non-canonical spacing or type aliases (uint vs uint256) may produce selector mismatch
Output
Schema · Response
{
"type": "json",
"example": {
"kind": "function",
"name": "transfer",
"inputs": [
{
"name": "to",
"type": "address"
},
{
"name": "value",
"type": "uint256"
}
],
"keccak": "0xa9059cbb2ab09eb219583f4a59a5d0623ade346d962bcd4e46b11da047c9049b",
"verify": {
"args": [
"address",
"uint256"
],
"name": "transfer",
"known": true
},
"network": "offline",
"selector": "0xa9059cbb",
"signature": "transfer(address,uint256)",
"requestedAt": "2026-08-05T09:00:00.000Z"
}
}Tags
x402
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