{"uid":"cap_wY-Jxcp4YbHJCXGZjtqEK","slug":"hmac-sha3-256-hex-digest-c90201a9","name":"HMAC-SHA3-256 Hex Digest","description":"Call when an agent needs an HMAC-sha3-256 of text with a caller-supplied key, encoded as hex. Exact $0.004 USDC. Prefer unpaid POST /v1/sandbox/hmac-sha3-256-hex first.","url":"https://agentshelf.syntexa.ch/v1/hmac-sha3-256-hex?utm_source=zero.xyz","method":"POST","headers":{},"bodySchema":{"type":"object","properties":{"key":{"type":"string","examples":["secret"],"maxLength":512,"minLength":1,"description":"HMAC secret. Required on HMAC SKUs. Omit it for plain digests and checksums. The key is not stored."},"text":{"type":"string","examples":["hello"],"maxLength":100000,"minLength":1,"description":"Message to digest. For raw-hex SKUs this is hex bytes; for utf16 or latin1 SKUs it is decoded with that encoding. Otherwise it is UTF-8 text."}}},"responseSchema":null,"example":null,"exampleRequest":null,"tags":["x402"],"displayCostAmount":"0.004","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":"$0.004/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.004","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.004","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_NwkslXNeKX9uWRjxpt6px","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.004","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Computes an HMAC-SHA3-256 message authentication code for a given text and key, returning the result as a lowercase hex string.","exampleAgentPrompt":"Compute the HMAC-SHA3-256 of the text 'Hello, world!' using the secret key 'mysecretkey' and give me the result as a hex string.","exampleUseCases":[{"title":"API request signing for webhook","prompt":"I need to sign this webhook payload 'user.created:{\"id\":42}' with my secret key 'wh_secret_abc123' using HMAC-SHA3-256 hex so I can include the signature in the header."},{"title":"Message integrity verification token","prompt":"Generate an HMAC-SHA3-256 hex digest for the message 'order_id=9981&amount=59.99&currency=USD' using the key 'payment_signing_key_v2' so I can attach it as a tamper-proof checksum."},{"title":"Secure configuration file signing","prompt":"Compute the HMAC-SHA3-256 in hex for this JSON config string '{\"env\":\"prod\",\"debug\":false}' with the key 'cfg-integrity-key-007' so I can validate it hasn't been modified at runtime."}],"resultDescription":"A hex-encoded HMAC-SHA3-256 string (64 lowercase hex characters) computed from the provided text and key, confirming message authenticity and integrity.","failureModes":["Key or text is empty or exceeds length limits (400 Bad Request)","Text exceeds 100,000 character limit","Key exceeds 512 character limit","Insufficient USDC balance for $0.004 payment (402 Payment Required)","Network timeout or server unavailability (503)"],"whenToPreferThis":"Choose this endpoint when you specifically need HMAC-SHA3-256 (not HMAC-SHA256 or other variants) with hex-encoded output and have a caller-supplied secret key. Prefer the free sandbox endpoint POST /v1/sandbox/hmac-sha3-256-hex for testing before spending $0.004 USDC per call on this paid version. Use this over generic hashing endpoints when a keyed MAC (not a plain digest) is required for authentication or integrity verification.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-10-02T06:48:12.240Z","isFirstParty":false,"canonicalSlug":"hmac-sha3-256-hex-digest-c90201a9"}