# SYNTHORA Agent Notary (Trust Layer EU)

> SYNTHORA Agent Notary (Trust Layer EU) is a paid API for AI agents from notary.hergertsynthora.com, paid per call via x402, $0.002/call, status unknown (last checked 2026-09-14).

Notarizes SHA-256 hashes and M2M execution/agreement records, returning Ed25519-signed receipts for tamper-evident proof-of-existence, proof-of-execution, and proof-of-agreement.

## Facts

- Endpoint: POST https://notary.hergertsynthora.com/service
- Price: $0.002/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/synthora-agent-notary-trust-layer-eu-421978af
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_IjXzYoO4k_GwolcbjPKGr

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 synthora-agent-notary-trust-layer-eu-421978af -d '<json body>'
```

Example prompt: Notarize this SHA-256 hash — a4f3c2b1...9d8e — using SYNTHORA's Trust Layer and give me the signed receipt ID I can use to verify it later.

## When to prefer this

Choose this endpoint when you need a lightweight, cryptographically-signed proof-of-existence or proof-of-execution record for M2M or agent-to-agent interactions, particularly in EU-regulated contexts. Prefer it over blockchain-based notarization when low cost ($0.002/call), low latency, and Ed25519-signed receipts are sufficient — and when you need a verify operation to later audit the same record. Best suited for AI agent pipelines that require audit trails without smart-contract overhead.

## Known failure modes

- Invalid or malformed SHA-256 hex string returns an error with the hash field
- Missing required fields for the chosen op (e.g. missing terms for agreement) returns a validation error
- Unknown or invalid receipt_id on verify returns a not-found or invalid receipt error
- Malformed op enum value returns an unsupported operation error
- Payment failure or insufficient USDC balance returns HTTP 402 before processing

## How this service works

Proof-of-existence, proof-of-execution and proof-of-agreement for M2M deals. Notarize a SHA-256, get an Ed25519-signed receipt anyone can verify later.

## Output

Returns a JSON object with ok:true, the operation kind (document, execution, or agreement), the SHA-256 digest, a human-readable certification statement issued by SYNTHORA Trust Layer, a unique receipt ID (prefixed nt-), and an ISO 8601 notarized_at timestamp. The receipt is Ed25519-signed and can be independently verified later using the verify operation.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "op": {
   "enum": [
    "notarize",
    "execution",
    "agreement",
    "verify"
   ],
   "type": "string",
   "description": "operation"
  },
  "hash": {
   "type": "string",
   "description": "sha256 hex (notarize/verify)"
  },
  "input": {
   "description": "execution input (execution)"
  },
  "terms": {
   "description": "agreement terms (agreement)"
  },
  "output": {
   "description": "execution output (execution)"
  },
  "content": {
   "description": "content to hash (notarize)"
  },
  "party_a": {
   "type": "string"
  },
  "party_b": {
   "type": "string"
  },
  "receipt_id": {
   "type": "string",
   "description": "nt-.. (verify)"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "ok": true,
  "niche": "notary",
  "result": {
   "kind": "document",
   "sha256": "..",
   "statement": "SYNTHORA Trust Layer certifies ...",
   "receipt_id": "nt-..",
   "notarized_at": "2026-07-10T00:00:00+00:00"
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/synthora-agent-notary-trust-layer-eu-421978af/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from notary.hergertsynthora.com](https://www.zero.xyz/host/notary.hergertsynthora.com/llms.txt)