{"uid":"cap_9fBPZtyhcWTDziiD0LQux","slug":"hmac-blake2b-512-hex-digest-fa1df3fe","name":"HMAC-BLAKE2b-512 Hex Digest","description":"Call when an agent needs an HMAC-blake2b512 of text with a caller-supplied key, encoded as hex. Exact $0.009 USDC. Prefer unpaid POST /v1/sandbox/hmac-blake2b512-hex first.","url":"https://agentshelf.syntexa.ch/v1/hmac-blake2b512-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":"0.009","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":"$0.009/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.009","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.009","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_9F-LP5RZ3eKuVMEE3DtvN","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.009","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Computes an HMAC using the BLAKE2b-512 hash function with a caller-supplied key and returns the result as a lowercase hex string","exampleAgentPrompt":"Compute an HMAC-BLAKE2b-512 of the text 'Hello, world!' using the key 'my-secret-key' and give me the result as hex.","exampleUseCases":[{"title":"Webhook payload integrity signing","prompt":"I need to sign this webhook payload 'user_id=42&event=purchase' with my secret key 'wh_secret_abc123' using HMAC-BLAKE2b-512 — can you compute the hex digest so I can attach it to the request?"},{"title":"API request authentication token","prompt":"Generate an HMAC-BLAKE2b-512 hex digest for the string 'GET /api/orders/2024-05-01' using the key 'api_signing_key_xyz' so I can authenticate the API call."},{"title":"Data tamper detection checksum","prompt":"Compute a keyed HMAC-BLAKE2b-512 hash of this JSON blob '{\"amount\":500,\"currency\":\"USD\"}' with the key 'integrity_key_99' so I can store it alongside the record and verify it hasn't been tampered with."}],"resultDescription":"A hex-encoded HMAC-BLAKE2b-512 string (128 hex characters representing 64 bytes) computed from the supplied text and key. No additional metadata is returned.","failureModes":["Missing or empty 'key' field returns a validation error","Missing or empty 'text' field returns a validation error","Key exceeding 512 characters returns a validation error","Text exceeding 100,000 characters returns a validation error","Payment failure (insufficient USDC) results in a 402 response"],"whenToPreferThis":"Choose this endpoint when you need a BLAKE2b-512-based HMAC (rather than SHA-256 or SHA-512 HMAC) and want hex output. BLAKE2b is faster than SHA-2 in software and provides equivalent security. Use the free sandbox endpoint POST /v1/sandbox/hmac-blake2b512-hex first to validate your integration before incurring the $0.009 USDC charge.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-10-02T06:50:20.466Z","isFirstParty":false,"canonicalSlug":"hmac-blake2b-512-hex-digest-fa1df3fe"}