# Agent Embassy — Prove URL Live (Signed Receipt)

> Agent Embassy — Prove URL Live (Signed Receipt) is a paid API for AI agents from agent-embassy.fly.dev, paid per call via x402, $0.25/call, status unknown (last checked 2026-10-11).

Fetches a given HTTPS URL and returns a signed, on-chain-verifiable receipt proving the page was live and returned HTTP 200 at a specific moment in time.

## Facts

- Endpoint: POST https://agent-embassy.fly.dev/v1/check/prove?utm_source=zero.xyz
- Price: $0.25/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-11
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/agent-embassy-prove-url-live-signed-receipt-6f10fa90
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_km2inNBRdKqW0dYxb0ckZ

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 agent-embassy-prove-url-live-signed-receipt-6f10fa90 -d '<json body>'
```

Example prompt: Can you prove that https://myproject.com/deliverable/report.pdf is live right now and give me a signed receipt I can share as evidence it existed?

## When to prefer this

Choose this endpoint when an AI agent needs tamper-evident, third-party-verifiable proof that a specific URL was live and returned HTTP 200 at a given moment — especially for smart contract conditions, freelance deliverable verification, audit trails, or any workflow where a human or system must independently verify that a web resource existed. Prefer this over a simple HTTP HEAD check when a signed, replayable receipt is required as evidence.

## Known failure modes

- URL times out after 10 seconds — returns failure verdict
- URL returns non-200 HTTP status — verdict is 'fail' rather than 'pass'
- URL body exceeds 1MB cap — fetch is truncated or rejected
- More than 3 redirects encountered — fetch aborted
- Idempotency key reuse — returns original receipt without re-running the action
- Published/known example idempotency keys are rejected
- Credentials embedded in the URL are rejected
- Payment failure via x402 — request not processed

## How this service works

Agents pay for work and prove what happened.

## Output

A JSON object containing: the tool name ('prove_it'), a chain array documenting the steps taken (request, authorization, action, proof, liability_boundary), a status field ('complete'), the payer account address, a verdict ('pass' or 'fail'), a unique receipt_id (e.g. 'emb_stu901'), and a receipt_version string ('embassy-receipt/1'). This receipt is signed and re-checkable, providing machine-verifiable proof of the URL's liveness at call time.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "url": {
   "type": "string",
   "description": "HTTPS URL to prove live (max 2000 chars; no credentials in URL). Fetched once; up to 3 redirects followed, 10s timeout, 1MB body cap. Default expectation: HTTP 200"
  },
  "idempotency_key": {
   "type": "string",
   "description": "Idempotency key: UUID v4, client-generated, one per logical request. Replaying the same key on this tool returns the original receipt — the action is not re-run, and the first request's receipt wins even if you resend different inputs. Published example keys are rejected. Keys are scoped per tool and per payer account: a key never returns another wallet's receipt."
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "tool": "prove_it",
  "chain": [
   "request",
   "authorization",
   "action",
   "proof",
   "liability_boundary"
  ],
  "status": "complete",
  "account": "0x1111111111111111111111111111111111111111",
  "verdict": "pass",
  "receipt_id": "emb_stu901",
  "receipt_version": "embassy-receipt/1"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/agent-embassy-prove-url-live-signed-receipt-6f10fa90/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from agent-embassy.fly.dev](https://www.zero.xyz/host/agent-embassy.fly.dev/llms.txt)