{"uid":"cap_bOeWNT5oiCDI87p15sQpa","slug":"event-topic0-from-solidity-event-signature-105f32e4","name":"Event topic0 from Solidity Event Signature","description":"Event topic0 from a Solidity event signature — Genesis402 / UnyKorn Operator Network","url":"https://twin.unykorn.org/abi-event-topic?utm_source=zero.xyz","method":"POST","headers":{},"bodySchema":{"type":"object","properties":{"params":{"type":"object","properties":{"signature":{"type":"string"}}}}},"responseSchema":{"type":"json","example":{"ok":true,"type":"abi-event-topic","receipt":{"tx_hash":"0x<64hex>","amount_usd":0.001,"receipt_id":"g402-<16hex>"},"generated_at":"<iso8601>"}},"example":null,"exampleRequest":null,"tags":["x402"],"displayCostAmount":"0.001","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":"$0.001/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.001","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.001","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_0k2PARiLalISqWd2x9pQ9","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.001","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Computes the keccak256 topic0 hash for a given Solidity event signature string","exampleAgentPrompt":"What is the topic0 hash for the Solidity event signature Transfer(address indexed from, address indexed to, uint256 value)?","exampleUseCases":[{"title":"Filter EVM logs by event type","prompt":"I need to filter Ethereum logs for Approval events — can you compute the topic0 for Approval(address indexed owner, address indexed spender, uint256 value) so I can use it as a log filter?"},{"title":"Verify event signature matches on-chain log","prompt":"I'm seeing a log on Ethereum with topic0 0xddf252ad... — can you compute the topic0 for Transfer(address,address,uint256) so I can confirm it matches?"},{"title":"Build event listener for DeFi protocol","prompt":"I'm setting up an event listener for a Uniswap pool and need the topic0 hash for Swap(address indexed sender, address indexed recipient, int256 amount0, int256 amount1, uint160 sqrtPriceX96, uint128 liquidity, int24 tick) — can you compute that?"}],"resultDescription":"Returns a JSON object with ok:true, the type field set to 'abi-event-topic', the computed topic0 keccak256 hex hash for the given event signature, a timestamp, and a payment receipt including transaction hash, USD amount, and receipt ID.","failureModes":["Invalid or malformed Solidity event signature returns an error response","Missing 'signature' param in request body causes a 400-level error","Payment failure via x402 protocol prevents execution","Network timeout on the UnyKorn operator node"],"whenToPreferThis":"Use this endpoint when you need to compute the keccak256 topic0 hash for a Solidity event signature to filter or identify EVM event logs, and you want a simple paid API call rather than running a local keccak256 library. Ideal for agents operating in blockchain contexts that need on-demand ABI encoding utilities without a full Ethereum node or local crypto library.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-10-01T18:55:42.649Z","isFirstParty":false,"canonicalSlug":"event-topic0-from-solidity-event-signature-105f32e4"}