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TraceFast Contract Function Selectors
x402
TraceFast Contract Function Selectors is a paid API for AI agents from mpp.tracefast.xyz, paid per call via x402, $0.005/call, status unknown (last checked 2026-10-12).
Returns the 4-byte function selectors found in an Ethereum contract's bytecode, each resolved to a known signature and name with a decode confidence status.
Price / call$0.005
Success—
StatusUnknown
How this service works
TraceFast live Ethereum data: the 4-byte function selectors found in a contract's bytecode, each resolved to a known signature and name where one exists, with how many known signatures share the selector. `decodeStatus` says how confident each resolution is. Path address: The contract address, `0x`-prefixed, 40 hex characters, any case. Docs: https://docs.tracefast.xyz/api/contract-selectors.md
Output
A list of 4-byte function selectors found in the contract's deployed bytecode. Each entry includes the hex selector, the resolved human-readable function signature and name (if a match exists in the known signature database), the number of known signatures that share that selector (indicating potential ambiguity), and a decodeStatus field indicating confidence level of the resolution.
Example use cases
Reverse-engineer unknown contract interface
“I have this Ethereum contract address 0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48 and no ABI — can you pull all its function selectors from the bytecode and tell me which function names they map to?”
Detect selector collisions in DeFi contract
“Check the contract at 0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D for any 4-byte selector conflicts — I want to know if any selectors match more than one known function signature.”
Audit smart contract callable methods
“For my security audit of the contract at 0x1f9840a85d5aF5bf1D1762F925BDADdC4201F984, give me a full list of its function selectors, their resolved names, and how confident TraceFast is about each one.”
Technical details
Endpoint
GEThttps://mpp.tracefast.xyz/api/v1/chains/1/contracts/:address/selectors?utm_source=zero.xyzWhen to prefer
Use this endpoint when you need to programmatically identify what functions a smart contract exposes without having its ABI, or when you want to verify selector-to-signature mappings including collision detection. Prefer over manual ABI lookups when the ABI is unavailable or unverified, or when you need machine-readable decodeStatus confidence signals for automated tooling.
Side effects
- Invalid or malformed contract address returns 400 error
- Address is an EOA (externally owned account) with no bytecode — returns empty selector list or error
- Undeployed or self-destructed contract address — no bytecode found
- Selector exists in bytecode but has no known signature match — resolved name will be null
- Network or upstream Ethereum node unavailability causing 503 or timeout
- Incorrect chain parameter causes lookup on wrong network
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| input | — |
Tags
x402
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