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FairSeal Notarize
x402
FairSeal Notarize is a paid API for AI agents from api.fairseal.io, paid per call via x402, $0.02/call, status unknown (last checked 2026-09-14).
Submits an agent decision, audit evidence, or probe record for cryptographic notarization, anchoring a SHA-256 payload hash in a Merkle batch on Base mainnet and returning a verifiable receipt.
Price / call$0.02
Success—
StatusUnknown
How this service works
Anchor an AI agent decision or audit record to Base mainnet. Submit {schema, payload_hash (SHA-256 hex, 64 chars), metadata}; service queues into a Merkle batch and returns a receipt with pending_anchor status immediately. Full Merkle proof and on-chain anchor_tx available via free GET /v1/notarize/:receipt_id after batch anchors (within batch_threshold receipts or 120s).
Output
A cryptographic receipt containing a receipt ID, Merkle proof, and on-chain anchor reference on Base mainnet. The receipt can be independently verified for free via GET /v1/notarize/:receipt_id, which returns the full Merkle proof and on-chain verification data.
Example use cases
Audit trail for autonomous trading agent
“Record this trade decision my agent just made on FairSeal — schema is 'trade_decision_v1', payload hash is 'b7e3a2d1...', and metadata includes the agent ID and timestamp — I need a receipt anchored on Base mainnet so we have an immutable audit log.”
Compliance evidence for AI model probe
“I need to notarize a model probe result for compliance purposes — use schema 'probe_record_v1', the SHA-256 hash of the probe payload is 'c4d9f2a8...', and include the evaluator ID and run timestamp in the metadata.”
Certify agent safety decision before deployment
“Before we deploy this agent update, notarize the safety review decision — schema 'safety_review_v1', payload hash 'e1b4c7f3...', metadata should include reviewer ID and decision outcome — I need the Merkle proof receipt for our records.”
Technical details
Endpoint
POSThttps://api.fairseal.io/v1/notarizeWhen to prefer
Choose FairSeal Notarize when you need a lightweight, low-cost ($0.02 USDC) cryptographic receipt anchored on Base mainnet for agent decisions, audit evidence, or probe records. Prefer this over general-purpose blockchain write operations when you want Merkle batch efficiency and a ready-made receipt lookup and proof API without managing your own smart contract or wallet infrastructure. Ideal for AI agent audit trails, compliance evidence, and tamper-proof decision logging in agentic workflows.
Side effects
- Invalid or missing payload_hash (not a valid SHA-256 hex string) — returns 400 Bad Request
- Missing required fields (schema or payload_hash) — returns 422 Unprocessable Entity
- Payment not provided or insufficient (requires $0.02 USDC via x402) — returns 402 Payment Required
- Base mainnet congestion causing delayed anchoring — receipt issued but on-chain confirmation may lag
- Duplicate payload hash submission — may create a new receipt for the same hash (not deduplicated)
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object |
Tags
x402
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