{"uid":"cap_W-_afvb4crOU9lLcyzkmn","slug":"solidity-function-event-selector-calculator-8db1a6e6","name":"Solidity Function/Event Selector Calculator","description":"Compute the 4-byte function/error selector and full keccak topic from a solidity signature, e.g. transfer(address,uint256). For decoding tx input prefixes and matching event topics. function selector, 4byte, method id, event topic, keccak signature Accepts payment on Base or Solana — either network works.","url":"https://api.x402node.dev/crypto/selector","method":"GET","headers":{},"bodySchema":{"type":"object","$schema":"https://json-schema.org/draft/2020-12/schema","required":["input"],"properties":{"input":{"type":"object","required":["type","method"],"properties":{"type":{"type":"string","const":"http"},"method":{"enum":["GET"],"type":"string"},"queryParams":{"type":"object","required":["signature"],"properties":{"signature":{"type":"string","description":"canonical signature, e.g. transfer(address,uint256) (required)"}}}},"additionalProperties":false}}},"responseSchema":null,"example":null,"exampleRequest":null,"tags":["x402"],"displayCostAmount":"0.01","displayCostAsset":"USDC","priceDynamic":false,"priceHint":null,"priceStatus":"priced","priceSource":"probe","requiresHandshake":false,"reviewCount":0,"rating":{"score":"0.00","successRate":"0.00","reviews":0,"stars":null,"state":"unrated"},"availabilityStatus":"unknown","priceObserved":null,"sessionDeposit":null,"pricing":{"kind":"static","summary":"$0.01/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.01","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.01","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_NSd8LxOTzKaSizdEfgaJ4","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.01","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Computes the 4-byte function selector and full keccak256 topic hash from a Solidity ABI signature string","exampleAgentPrompt":"What's the 4-byte function selector and full keccak256 topic hash for the Solidity signature transfer(address,uint256)?","exampleUseCases":null,"resultDescription":"Returns the 4-byte hex function selector (first 4 bytes of keccak256 of the signature) and the full 32-byte keccak256 topic hash, suitable for matching transaction input prefixes and EVM event topics","failureModes":["Invalid or malformed Solidity signature string returns an error","Missing signature parameter returns a 400 bad request","Network timeout or service unavailability returns a 5xx error","Ambiguous signature with incorrect parameter types may return unexpected selector"],"whenToPreferThis":"Use this endpoint when you need to programmatically compute Solidity function selectors or event topic hashes from ABI signatures without running a local Ethereum toolchain or web3 library. Ideal for decoding raw transaction inputs, filtering event logs by topic0, or building ABI-aware transaction parsers on the fly.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-09-14T06:58:44.707Z","isFirstParty":false}