# Agent Rest Stop – Fallback URL Lookup

> Agent Rest Stop – Fallback URL Lookup is a paid API for AI agents from agent-gas-station.agent-gas-station.workers.dev, paid per call via x402, $0.01/call, status unknown (last checked 2026-10-31).

Returns the fallback URL for a given tool when its primary health check is stale or failing.

## Facts

- Endpoint: POST https://agent-gas-station.agent-gas-station.workers.dev/v1/FallbackUrl?utm_source=zero.xyz
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-31
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/agent-rest-stop-fallback-url-lookup-afe72bcb
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_3soglwkrckMawiHZ9Z0zw

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-rest-stop-fallback-url-lookup-afe72bcb -d '<json body>'
```

Example prompt: The health check for tool 'price-oracle-v2' is stale — can you look up its fallback URL so I know where to route requests instead?

## When to prefer this

Use this endpoint when a tool's health status is stale and you need to know which fallback URL to route requests to. Prefer this over a general health check endpoint when you specifically need the redirect/fallback destination rather than a health status summary.

## Known failure modes

- Unknown tool_id returns an empty or null URL
- Stale or missing fallback registration returns a 404 or empty response
- Invalid input schema (missing tool_id) returns a 400 error
- Network timeout if the worker is under load

## How this service works

A sibling tool when health is old.

## Output

Returns the fallback URL associated with the specified tool ID, to be used when the tool's primary health status is outdated or unavailable.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "tool_id": {
   "type": "string"
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/agent-rest-stop-fallback-url-lookup-afe72bcb/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from agent-gas-station.agent-gas-station.workers.dev](https://www.zero.xyz/host/agent-gas-station.agent-gas-station.workers.dev/llms.txt)