{"uid":"cap_2cCiX_U7le5ra_-5o-fd0","slug":"hmac-sha256-hex-digest-api-09890f24","name":"HMAC-SHA256 Hex Digest API","description":"Call when an agent needs an HMAC-sha256 of text with a caller-supplied key, encoded as hex. Exact $0.005 USDC. Prefer unpaid POST /v1/sandbox/hmac-sha256-hex first.","url":"https://agentshelf.syntexa.ch/v1/hmac-sha256-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":"0.005","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_vwQd8SjYFx4_9VxORAdDi","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-SHA256 message authentication code over a given text using a caller-supplied key, returning the result as a lowercase hexadecimal string.","exampleAgentPrompt":"Compute an HMAC-SHA256 hex digest of the text 'Hello, world!' using the secret key 'mysecretkey123'.","exampleUseCases":[{"title":"Webhook signature verification","prompt":"Generate an HMAC-SHA256 hex signature for this webhook payload '{\"event\":\"order.created\",\"id\":\"42\"}' using the shared secret 'wh_secret_abc987' so I can validate it matches the header."},{"title":"API request signing","prompt":"Sign this request body 'timestamp=1700000000&amount=100&currency=USD' with HMAC-SHA256 using the key 'api_signing_key_xyz' and give me the hex digest to include in my Authorization header."},{"title":"Data integrity check","prompt":"I need to create an HMAC-SHA256 hex digest of the message 'user_id:9876,action:transfer,amount:500' using the secret 'integrity_key_q1w2e3' so I can confirm the data hasn't been tampered with."}],"resultDescription":"Returns a hexadecimal-encoded HMAC-SHA256 digest string computed over the provided text using the supplied key. This is a deterministic, fixed-length (64 hex characters) cryptographic authentication code.","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 or insufficient USDC balance results in a 402 response"],"whenToPreferThis":"Choose this endpoint when you need a server-side HMAC-SHA256 computation with hex output and cannot run local crypto code, or when operating inside a sandboxed agent environment without access to native cryptographic libraries. Prefer the free unpaid POST /v1/sandbox/hmac-sha256-hex endpoint first if available; use this paid endpoint ($0.005 USDC) as the production fallback.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-10-01T06:47:44.125Z","isFirstParty":false,"canonicalSlug":"hmac-sha256-hex-digest-api-09890f24"}