# witnessd.vip Witness Endpoint

> witnessd.vip Witness Endpoint is a paid API for AI agents from witnessd.vip, paid per call via x402, $0.02/call, status unknown (last checked 2026-10-11).

Independently fetches, hashes, timestamps, and Merkle-anchors any URL or API response on Base as a neutral third-party witness record

## Facts

- Endpoint: POST https://witnessd.vip/api/witness?utm_source=zero.xyz
- Price: $0.02/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-11
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/witnessd-vip-witness-endpoint-b9437ac8
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_d6reekuRX8dj4xK2B_RER

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 witnessd-vip-witness-endpoint-b9437ac8 -d '<json body>'
```

Example prompt: Can you create an independent timestamped witness record of what https://api.example.com/prices returns right now — I need a neutral third-party proof anchored on Base that I can use as an audit trail?

## When to prefer this

Choose this endpoint when you need a neutral, independent, blockchain-anchored proof that a specific URL or API endpoint had particular content at a specific moment in time — especially for audit trails, legal evidence, compliance snapshots, or AI agent output verification. Prefer this over simple screenshots or self-hosted archiving when tamper-proof third-party attestation and Merkle anchoring on Base are required. Best suited for single-URL, point-in-time witnessing rather than ongoing monitoring.

## Known failure modes

- Target URL is unreachable or returns a non-2xx status — witness may still be created but content reflects the error response
- Invalid or malformed URL input — API returns a validation error
- Payment of $0.02 USDC not fulfilled via x402 — request rejected before fetch is attempted
- Target URL requires authentication or blocks external fetchers — returns partial or access-denied content
- Network timeout on the target URL — witness may record a timeout rather than content

## How this service works

Independently fetch, hash, timestamp and archive a URL or API response; returns a signed certificate. Merkle-anchored on Base hourly. Neutral third-party evidence for agent commerce disputes.

## Output

Returns a JSON object containing a unique witness ID (e.g. ws_76cae2b76822b099d37882c4), a retrieve_url to access the archived response content, and a certificate_url linking to the Merkle-anchored proof on Base that verifies the fetch was performed at a specific time by a neutral third party.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "url": {
   "type": "string",
   "format": "uri",
   "description": "The http(s) URL or API endpoint to witness right now"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "id": "ws_76cae2b76822b099d37882c4",
  "retrieve_url": "https://witnessd.vip/api/retrieve/ws_76cae2b76822b099d37882c4",
  "certificate_url": "https://witnessd.vip/api/certificate/ws_76cae2b76822b099d37882c4"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/witnessd-vip-witness-endpoint-b9437ac8/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from witnessd.vip](https://www.zero.xyz/host/witnessd.vip/llms.txt)