{"uid":"cap_4hoBVv2tOTJT5SOBpIxP0","slug":"hmac-sha256-base64-signing-747c9e74","name":"HMAC-SHA256 Base64 Signing","description":"Call when an agent needs an HMAC-sha256 of text with a caller-supplied key, encoded as base64. Exact $0.006 USDC. Prefer unpaid POST /v1/sandbox/hmac-sha256-base64 first.","url":"https://agentshelf.syntexa.ch/v1/hmac-sha256-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":"0.006","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":"$0.006/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.006","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.006","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_epoILXLSSor2TSXrHb1QS","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.006","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Computes an HMAC-SHA256 digest of a given text string using a caller-supplied key and returns the result encoded as base64.","exampleAgentPrompt":"Compute the HMAC-SHA256 of the text 'Hello, World!' using the secret key 'my-secret-key' and give me the result as a base64-encoded string.","exampleUseCases":[{"title":"Webhook payload signature verification","prompt":"I need to sign this webhook payload 'user.created:{\"id\":42}' with our secret key 'wh_secret_abc123' using HMAC-SHA256 and return the base64 result so I can attach it as the X-Signature header."},{"title":"API request HMAC authentication","prompt":"Generate an HMAC-SHA256 base64 signature for the string 'GET /api/orders/9981 timestamp=1718000000' using the key 's3cr3tApiKey' so I can authenticate this API request."},{"title":"Message integrity token for data pipeline","prompt":"Sign this JSON blob '{\"event\":\"transfer\",\"amount\":500}' with the key 'pipeline-signing-key-2024' using HMAC-SHA256 and encode it in base64 — I need to attach it as an integrity token before sending it downstream."}],"resultDescription":"Returns a base64-encoded HMAC-SHA256 digest string computed from the provided text using the given key. The response is a compact, portable signature suitable for use in headers, tokens, or integrity checks.","failureModes":["Missing or empty key or text fields returns a validation error","Text exceeding 100,000 characters or key exceeding 512 characters is rejected","Payment failure (insufficient USDC balance or x402 protocol error) prevents the call","Network timeout or service unavailability returns a 5xx error"],"whenToPreferThis":"Use this endpoint when your agent needs a quick, pay-per-use HMAC-SHA256 base64 computation without setting up a local cryptographic library or managing infrastructure. Prefer the unpaid sandbox endpoint (POST /v1/sandbox/hmac-sha256-base64) for testing and development; use this paid endpoint for production workloads or when the sandbox is unavailable. It is ideal for signing webhook payloads, generating API authentication headers, or producing message integrity tokens on demand within an agentic workflow.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-10-02T06:49:01.197Z","isFirstParty":false,"canonicalSlug":"hmac-sha256-base64-signing-747c9e74"}