Function selectors of a contract

Open the contract on its entity page →

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.

GET https://tracefast.xyz/api/v1/chains/1/contracts/{address}/selectors

Parameter	In	Type	Notes
`address`	path	string	`0x`-prefixed, 40 hex characters, any case

Access — an API key on the Enriched Data plan or higher (plans), or no key at all: pay per call with x402 at the same path on https://mpp.tracefast.xyz/api/v1, at the price its 402 states. As a tool for AI agents: get_contract_selectors on the MCP server. Stable — see stability.

chains/1 is a literal: other chain ids answer 404 chain_not_supported. The method takes no query parameters — an unknown one is refused rather than ignored.

What it covers, and what it does not

Selectors come from the bytecode, not from a verified source or an ABI. A proxy answers with its own selectors, not its implementation's: ask this method about the implementation address from the proxy method.
A signature is a best match, not proof. A selector is only 4 bytes, and unrelated signatures collide. When candidateCount is above 1, signature is the most common known one. The 0xffffffff row in the example below is such a match: the name is a known collision, not a function the contract declares.
abi_missing is not "no function". The selector is in the code; no known signature has it.

Response

200 application/json, the USDC proxy:

{
  "data": {
    "chainId": 1,
    "address": "0xa0b86991c6218b36c1d19d4a2e9eb0ce3606eb48",
    "codeHash": "0xd80d4b7c890cb9d6a4893e6b52bc34b56b25335cb13716e0d1d31383e6b41505",
    "selectorCount": 6,
    "selectors": [
      { "selector": "0x8f283970", "signature": "changeAdmin(address)", "name": "changeAdmin", "candidateCount": 2, "decodeStatus": "ambiguous" },
      { "selector": "0xf851a440", "signature": "admin()", "name": "admin", "candidateCount": 1, "decodeStatus": "partial" },
      { "selector": "0xffffffff", "signature": "LOCK8605463013()", "name": "LOCK8605463013", "candidateCount": 3, "decodeStatus": "ambiguous" },
      { "selector": "0x3659cfe6", "signature": "upgradeTo(address)", "name": "upgradeTo", "candidateCount": 2, "decodeStatus": "ambiguous" },
      { "selector": "0x4f1ef286", "signature": "upgradeToAndCall(address,bytes)", "name": "upgradeToAndCall", "candidateCount": 2, "decodeStatus": "ambiguous" },
      { "selector": "0x5c60da1b", "signature": "implementation()", "name": "implementation", "candidateCount": 1, "decodeStatus": "partial" }
    ]
  },
  "meta": {
    "chain": "ethereum",
    "timestamp": 1789047625629,
    "cached": false,
    "docs": "https://docs.tracefast.xyz/api/contract-selectors"
  }
}

`data`

Field	Meaning
`chainId`	`1` — Ethereum mainnet
`address`	the contract, lowercase
`codeHash`	hash of the code the selectors were read from
`selectorCount`	how many selectors were found
`selectors[]`	every selector, each with its resolution

A selector

Field	Meaning
`selector`	the 4-byte selector, `0x`-prefixed
`signature`	the canonical signature, for example `transfer(address,uint256)`. Absent when no known signature has this selector, or when the only one known is malformed
`name`	the function name alone, present whenever the selector is named. It can be present without `signature`: when the only known signature is malformed (say `transfer(address uint256)`), only the name is served
`candidateCount`	how many known signatures share the selector. `1` is unambiguous
`decodeStatus`	`partial` — one known signature, parameter names unknown; `ambiguous` — several known signatures share the selector; `abi_missing` — no known signature

How a selector is derived from a function signature: ethereum.org — smart contract ABI.

Errors

Status	`code`	When	`details`
404	`not_found`	no contract code is indexed at this address	—
422	`block_not_available`	`reason: coverage_gap` — recent blocks are in a coverage gap, and a contract deployed in them cannot be seen right now. Retry later	`coverageGapFromBlock`, `coverageGapToBlock`, `maxAvailableBlock`

Malformed input, unknown parameters and the key check's 401/403/429 are the same for every method — see conventions and API keys.

One contract — selectorCount and the ERC-20 interface read from these selectors
Bytecode of a contract — the code they were read from
Implementations of a proxy contract — where a proxy's real functions live
Contracts on the entity page — the same contract, read in the app

Last updated 22 Oct 2026, 08:06 UTC · verified against TraceFast v1.0.261 · Markdown