# SignalHarness Content Fingerprint > SignalHarness Content Fingerprint is a paid API for AI agents from signalharness.ai, paid per call via x402, $0.005/call, status unknown (last checked 2026-09-14). Computes a SHA-256 cryptographic fingerprint and byte-count of submitted content (HTML, JSON, text, or base64 binary) with normalization metadata for deduplication and integrity verification. ## Facts - Endpoint: POST https://signalharness.ai/api/agent/services/content_fingerprint/invoke - Price: $0.005/call - Payment: x402 - Status: unknown - Last checked: 2026-09-14 - Activations on Zero: 0 - Tags: x402 - Canonical page: https://www.zero.xyz/c/signalharness-content-fingerprint-999f5fc9 - Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_0fAhpfp-LQFVzZmYJKnmx Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently. ## How to call it through Zero Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`): ```sh zero fetch --capability signalharness-content-fingerprint-999f5fc9 -d '' ``` Example prompt: Can you fingerprint this HTML string for me and give me its SHA-256 hash plus a normalized hash so I can detect duplicates? Here's the content: '

Hello World

' ## When to prefer this Choose this endpoint when you need a cryptographic fingerprint of arbitrary content (HTML, JSON, text, or binary) for deduplication, change detection, caching keys, or integrity verification — especially in agent workflows requiring per-call micropayment via x402/USDC. Prefer this over ad-hoc client-side hashing when you need server-side normalization (e.g., stripping whitespace from HTML before hashing) to ensure semantically equivalent content produces the same fingerprint. ## Known failure modes - Input content exceeds 65,536 character/byte limit — request rejected - No valid content field provided (html, json, text, or base64 all absent) — validation error - Invalid base64 encoding pattern — schema validation failure - Payment failure or insufficient USDC balance — 402 Payment Required - Malformed JSON body — 400 Bad Request ## How this service works Explore 330 pay-per-call x402 API services and 27 agent-native digital products, with Base USDC pricing, secure Polar checkout, and free discovery. ## Output Returns a JSON object containing: a SHA-256 hash of the raw content, a normalized SHA-256 hash (after applying a normalization strategy), the raw byte count, the normalization method name, the normalized content length, and a replay flag indicating if this is a repeated computation. Also includes a payment receipt with execution metadata, timing, and settlement reference. ## Request schema (JSON Schema) ```json { "type": "object", "properties": { "html": { "type": "string", "maxLength": 65536, "minLength": 1 }, "json": { "type": [ "object", "array", "string", "number", "boolean", "null" ] }, "text": { "type": "string", "maxLength": 65536, "minLength": 0 }, "type": { "type": "string", "maxLength": 128, "minLength": 1 }, "base64": { "type": "string", "pattern": "^[A-Za-z0-9+/]*={0,2}$", "maxLength": 65536, "minLength": 0 } } } ``` ## Response schema (JSON Schema) ```json { "type": "json", "example": { "replay": false, "result": { "type": "example", "sha256": "0000000000000000000000000000000000000000000000000000000000000000", "byteCount": 0, "normalization": "example", "normalizedLength": 0, "normalizedSha256": "0000000000000000000000000000000000000000000000000000000000000000" }, "status": "succeeded", "receipt": { "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913", "usage": [], "status": "succeeded", "network": "eip155:8453", "artifacts": [], "endedAtMs": 0, "latencyMs": 0, "paymentId": "example-payment", "receiptId": "example-receipt", "requestId": "example-request", "serviceId": "content_fingerprint", "executionId": "example-execution", "startedAtMs": 0, "amountAtomic": "5000", "resultSha256": "3861c2f5ca83c78359f3fc168c79d4dab10e7dc1d28858e724e9f33d397cb3b1", "serviceVersion": "1.0.0", "settlementReference": "0x0000000000000000000000000000000000000000000000000000000000000000" }, "artifacts": [], "requestId": "example-request", "executionId": "example-execution" } } ``` ## More - Live health (JSON, refreshed every minute): https://www.zero.xyz/c/signalharness-content-fingerprint-999f5fc9/health.json - [Zero catalog index](https://www.zero.xyz/llms.txt) - [Other services from signalharness.ai](https://www.zero.xyz/host/signalharness.ai/llms.txt)