# Immuta Seal – On-Chain Document Notarization

> Immuta Seal – On-Chain Document Notarization is a paid API for AI agents from api.immuta.app, paid per call via x402, $1/call, status unknown (last checked 2026-09-16).

Notarizes a SHA-256 hash on the blockchain, creating a permanent, independently verifiable timestamp proof that a document existed at a specific moment.

## Facts

- Endpoint: POST https://api.immuta.app/seal
- Price: $1/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-16
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/immuta-seal-on-chain-document-notarization-07e57ea8
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_2X5m-engdg2xnpO_HZstM

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 immuta-seal-on-chain-document-notarization-07e57ea8 -d '<json body>'
```

Example prompt: I need to notarize this file — its SHA-256 hash is e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855. Seal it on the blockchain so I have permanent proof it existed right now.

## When to prefer this

Choose this endpoint when you need a cryptographically secure, blockchain-anchored timestamp proving a document or file existed at a specific moment — without ever transmitting the document itself. Ideal for legal evidence, IP authorship records, compliance audit trails, or any workflow requiring tamper-proof, independently verifiable proof of existence. Prefer this over centralized notarization services when trustlessness and decentralization matter.

## Known failure modes

- Invalid or malformed SHA-256 hash format — returns 400 Bad Request
- Insufficient USDC balance or payment failure — transaction not submitted
- Blockchain network congestion causing delayed confirmation
- Duplicate hash submission — may succeed but creates a second on-chain record
- Network timeout before transaction is mined — receipt may not be returned even if transaction was broadcast

## How this service works

Notarize a document on-chain: permanent, independently verifiable proof that a SHA-256 hash existed at this moment. Send only the hash - the document never leaves your system. Returns a blockchain transaction receipt.

## Output

Returns a blockchain transaction receipt confirming the hash has been permanently anchored on-chain, including the transaction hash, block number, timestamp, and network details — providing independently verifiable proof that the given SHA-256 hash existed at that exact moment.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "note": {
   "type": "string",
   "maxLength": 500,
   "description": "Optional note stored on-chain (up to 500 bytes)"
  },
  "label": {
   "type": "string",
   "maxLength": 100,
   "description": "Short label stored on-chain with the record (1-100 bytes)"
  },
  "sha256": {
   "type": "string",
   "pattern": "^[0-9a-fA-F]{64}$",
   "description": "SHA-256 hash (64 hex chars) of the document to notarize. Compute locally; do not send the document."
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/immuta-seal-on-chain-document-notarization-07e57ea8/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.immuta.app](https://www.zero.xyz/host/api.immuta.app/llms.txt)