{"uid":"cap_Dyzs3df5gJagrgBHFxRNi","slug":"keccak-256-hash-via-fastx402-abadff99","name":"Keccak-256 Hash via FastX402","description":"146 pay-per-call tools for AI agents, from $0.001 per request in USDC on Base or Solana with x402. No account, no API key.","url":"https://fastx402.tools/keccak256?utm_source=zero.xyz","method":"GET","headers":{},"bodySchema":{"type":"object","$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":[],"properties":{"hex":{"type":"string","description":"Hex bytes to hash, like 0x68656c6c6f; \"0x\" is empty"},"text":{"type":"string","description":"UTF-8 text to hash"}}}},"additionalProperties":false},"output":{"type":"object","required":["type"],"properties":{"type":{"type":"string"},"example":{"type":"object","properties":{"hash":{"type":"string"},"input_bytes":{"type":"integer"}}}}}}},"responseSchema":{"type":"json","example":{"hash":"0x1c8aff950685c2ed4bc3174f3472287b56d9517b9c948127319a09a7a36deac8","input_bytes":5}},"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_-hPtFzF984ZJyLwdmVIT2","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 Keccak-256 (Ethereum-native SHA-3) hash of a UTF-8 string or hex-encoded bytes, returning the hex digest and input byte count.","exampleAgentPrompt":"What's the Keccak-256 hash of the text 'Transfer(address,address,uint256)'? I need it to get the Ethereum event topic hash.","exampleUseCases":[{"title":"Solidity event topic hash","prompt":"Give me the Keccak-256 hash of 'Transfer(address,address,uint256)' so I can use it as the event topic in my Ethereum log filter."},{"title":"Hash hex-encoded contract calldata","prompt":"Compute the Keccak-256 hash of the hex bytes 0x68656c6c6f and tell me how many bytes the input was."},{"title":"Verify smart contract function selector","prompt":"Hash the text 'approve(address,uint256)' with Keccak-256 — I want to check the first 4 bytes match the function selector in this transaction calldata."}],"resultDescription":"A JSON object containing 'hash' (the 0x-prefixed 64-character Keccak-256 hex digest) and 'input_bytes' (the number of bytes consumed from the input), e.g. {\"hash\":\"0x1c8aff...\",\"input_bytes\":5}.","failureModes":["Missing both 'hex' and 'text' query params — server returns an error indicating input is required","Malformed hex string (odd length or non-hex characters) — parsing error returned","Payment not provided or insufficient — 402 Payment Required response before computation occurs","Empty 0x input treated as empty bytes, returning the Keccak-256 of zero bytes"],"whenToPreferThis":"Choose this endpoint when you need the Keccak-256 (Ethereum-native) variant of SHA-3 specifically — not standard SHA-3/FIPS-202, which uses different padding. Ideal for Ethereum development tasks such as computing event topic hashes, function selectors, address derivation checks, or any on-chain data verification. No API key or account required; payment is per-call via USDC on Base.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-10-17T12:41:00.977Z","isFirstParty":false,"canonicalSlug":"keccak-256-hash-via-fastx402-abadff99"}