{"uid":"cap_2woLViOpTb76stzIyJIKp","slug":"hmac-sha3-256-base64-signing-97547599","name":"HMAC-SHA3-256 Base64 Signing","description":"Call when an agent needs an HMAC-sha3-256 of text with a caller-supplied key, encoded as base64. Exact $0.005 USDC. Prefer unpaid POST /v1/sandbox/hmac-sha3-256-base64 first.","url":"https://agentshelf.syntexa.ch/v1/hmac-sha3-256-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":"0.005","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":"$0.005/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.005","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.005","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_Ee_oRHR9wSlZulrltNCsK","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.005","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 using a caller-supplied key and returns the result encoded as base64.","exampleAgentPrompt":"Compute an HMAC-SHA3-256 of the text 'order-id:98765' using the key 'mysecretkey2024' and give me the result as base64.","exampleUseCases":[{"title":"Webhook payload integrity signing","prompt":"I need to sign the webhook payload 'user_created:{\"id\":42,\"email\":\"alice@example.com\"}' with the key 'wh_secret_prod_abc123' using HMAC-SHA3-256 and get the base64 result to include in the X-Signature header."},{"title":"API request authentication token","prompt":"Generate an HMAC-SHA3-256 base64 signature for the string 'GET:/api/v2/orders:1717200000' using the key 'api_signing_key_xyz' so I can authenticate this API request."},{"title":"Data integrity check for stored record","prompt":"Compute the HMAC-SHA3-256 of 'transaction:TXN-20240601-8812,amount:250.00,currency:USD' with the key 'integrity_check_key_prod' and return it as base64 so I can store it alongside the record."}],"resultDescription":"Returns a base64-encoded HMAC-SHA3-256 digest string computed from the provided text and key. The output is a standard base64 string representing the 256-bit message authentication code.","failureModes":["Empty or missing key (minLength:1 violated) returns a validation error","Empty or missing text (minLength:1 violated) returns a validation error","Text exceeding 100,000 characters returns a payload-too-large error","Key exceeding 512 characters returns a validation error","Payment of exactly $0.005 USDC required; insufficient funds returns 402","Network timeout on the paid endpoint — retry with the free sandbox endpoint at /v1/sandbox/hmac-sha3-256-base64"],"whenToPreferThis":"Choose this endpoint when you need HMAC-SHA3-256 specifically (not SHA-256, SHA-384, or other HMAC variants) and require the output as standard base64 encoding. Prefer it over the sandbox endpoint when the computation must be performed in a production billing context. Use the sibling SHA-384/base64url endpoint if you need the SHA-384 algorithm or base64url encoding instead of base64.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-10-02T06:50:03.571Z","isFirstParty":false,"canonicalSlug":"hmac-sha3-256-base64-signing-97547599"}