# Citiview Blockchain Timestamp (OpenTimestamps)

> Citiview Blockchain Timestamp (OpenTimestamps) is a paid API for AI agents from agents.citiviewgroup.com, paid per call via x402, $0.01/call, status unknown (last checked 2026-10-14).

Anchors the SHA-256 hash of any text, file, or URL in the Bitcoin blockchain via OpenTimestamps calendars and returns a .ots proof file for later verification

## Facts

- Endpoint: GET https://agents.citiviewgroup.com/v1/timestamp?utm_source=zero.xyz
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/citiview-blockchain-timestamp-opentimestamps-413be52f
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_SzSacH2athDqLdygxJmrI

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 citiview-blockchain-timestamp-opentimestamps-413be52f
```

Example prompt: Can you anchor the hash of this contract text in the Bitcoin blockchain and give me the .ots proof file so I can prove it existed today? The text is: 'This agreement between Acme Corp and Beta LLC is dated June 1 2025.'

## When to prefer this

Choose this endpoint when you need cryptographic, decentralized proof of existence anchored to the Bitcoin blockchain without relying on any central authority. Ideal for legal notarization, intellectual property protection, contract timestamping, or any scenario requiring trustless verification that data existed at a specific point in time. Prefer over centralized timestamping services when immutability and third-party-verifiability via the open OpenTimestamps protocol are required.

## Known failure modes

- Invalid or malformed SHA-256 hash returns an error
- Base64-encoded content that is too large may be rejected
- Inaccessible URL (404, timeout) cannot be fetched and hashed
- OpenTimestamps calendar servers temporarily unavailable causing delay
- Missing required input field (text, url, sha256, or content_base64) returns validation error

## How this service works

Proof of existence: anchor the SHA-256 of any text, file or URL in the Bitcoin blockchain through OpenTimestamps calendars and get the .ots proof file, so anyone can later verify the data existed at that time. Also callable as GET with the same fields as query parameters.

## Output

A .ots (OpenTimestamps) proof file containing cryptographic attestation that links the SHA-256 hash of the submitted content to a Bitcoin blockchain block, allowing anyone to independently verify that the data existed at the timestamped moment using the OpenTimestamps protocol.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "properties": {
      "url": {
       "type": "string"
      },
      "text": {
       "type": "string"
      },
      "sha256": {
       "type": "string"
      },
      "content_base64": {
       "type": "string"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/citiview-blockchain-timestamp-opentimestamps-413be52f/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from agents.citiviewgroup.com](https://www.zero.xyz/host/agents.citiviewgroup.com/llms.txt)