{"uid":"cap_vUmYHvNQ6d2yEeAAWL3Wx","slug":"hmac-blake2b-512-base64-signing-7ee44944","name":"HMAC-BLAKE2b-512 Base64 Signing","description":"Call when an agent needs an HMAC-blake2b512 of text with a caller-supplied key, encoded as base64. Exact $0.01 USDC. Prefer unpaid POST /v1/sandbox/hmac-blake2b512-base64 first.","url":"https://agentshelf.syntexa.ch/v1/hmac-blake2b512-base64?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":"0.01","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_PRDqXr_-wqfzJyIwLNfpP","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 an HMAC using the BLAKE2b-512 hash function with a caller-supplied key and returns the result encoded as base64","exampleAgentPrompt":"Compute an HMAC-BLAKE2b-512 of the text 'Hello, world!' using the key 'my-secret-key' and give me the result as base64.","exampleUseCases":[{"title":"API webhook signature verification","prompt":"I need to sign the webhook payload '{\"event\":\"payment.completed\",\"amount\":100}' with my secret key 'whsec_abc123' using HMAC-BLAKE2b-512 and get the base64 output so I can include it in the request header."},{"title":"Message integrity tagging for agent logs","prompt":"Take this log message 'Agent run #4821 completed at 2024-06-01T12:00:00Z with 3 actions' and sign it with the key 'log-signing-key-v2' using HMAC-BLAKE2b-512, give me the base64 MAC so I can store it alongside the log entry."},{"title":"Secure token generation for internal auth","prompt":"Generate an HMAC-BLAKE2b-512 base64 signature for the string 'user_id=9982&expires=1717200000' using the key 'internal-token-secret' so I can use it as a tamper-proof auth token."}],"resultDescription":"Returns a base64-encoded HMAC-BLAKE2b-512 digest computed over the provided text using the supplied key. The output is a fixed-length base64 string representing the 512-bit MAC.","failureModes":["Empty or missing key returns a validation error","Text exceeds 100,000 character limit returns a payload-too-large error","Missing required fields (key or text) returns a 400 bad request","Network or service unavailability returns a 5xx error","Payment failure (insufficient USDC balance) blocks the request via x402 protocol"],"whenToPreferThis":"Use this endpoint when you specifically need BLAKE2b-512 as the underlying hash function for an HMAC operation — preferred over SHA-256 HMAC when higher performance or longer digest length is required. Choose this when the consuming system expects BLAKE2b-512 signatures specifically. For free or sandbox testing, prefer the unpaid POST /v1/sandbox/hmac-blake2b512-base64 endpoint first.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-10-02T06:50:10.446Z","isFirstParty":false,"canonicalSlug":"hmac-blake2b-512-base64-signing-7ee44944"}