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Solidity Function Selector and Event Topic0 Generator
x402
Solidity Function Selector and Event Topic0 Generator is a paid API for AI agents from flat-rate-llm.kikoribera03.workers.dev, paid per call via x402, $0.0025/call, status unknown (last checked 2026-09-15).
Converts a canonical Solidity function or event signature into its 4-byte function selector and 32-byte event topic0 hash.
Price / call$0.0025
Success—
StatusUnknown
How this service works
60 paid endpoints with no metering, no API key and no account. Each endpoint has one flat price per call, whatever the size of the request: LLM completions with automatic failover across several large models, read-only EVM tooling over Base, Ethereum, Polygon, Arbitrum and Optimism, and pure crypto utilities that touch no network.
Output
Returns a JSON object with two fields: 'selector' (the 4-byte hex function selector, e.g. 0xa9059cbb) and 'topic0' (the 32-byte hex keccak256 hash of the signature, used as the first topic when filtering event logs).
Example use cases
Building raw EVM calldata by hand
“I need to craft raw calldata for an approve call on an ERC20 — can you give me the 4-byte selector for approve(address,uint256)?”
Filtering smart contract event logs
“I want to filter Ethereum logs for Transfer events on an ERC20 — what's the topic0 hash for Transfer(address,address,uint256)?”
Verifying ABI selector for a custom contract
“I wrote a custom function called swapExactTokensForETH(uint256,uint256,address[],address,uint256) — what's its 4-byte selector so I can double-check my ABI encoding?”
Technical details
Endpoint
POSThttps://flat-rate-llm.kikoribera03.workers.dev/v1/util/selectorWhen to prefer
Use this endpoint when you need to programmatically compute EVM function selectors or event topic0 hashes without running a local Solidity compiler or ABI library. Ideal for agents building raw calldata, filtering event logs, or verifying ABI encodings on the fly. Prefer this over a full ABI-parsing library when you only need the selector or topic0 and want a stateless, pay-per-call REST call.
Side effects
- Missing or malformed 'signature' parameter returns an error — signature must be canonical (no spaces, no argument names, e.g. transfer(address,uint256))
- Passing a non-canonical form such as 'transfer(address _to, uint256 _value)' may return incorrect results or an error
- Network or upstream worker timeout may return a 5xx error
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| signaturerequired | string | Canonical signature: name(type1,type2), no spaces and no argument names. |
Output
Schema · Response
| Field | Type | Description |
|---|---|---|
| topic0 | string | |
| selector | string |
Tags
x402
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