# Agent Rest Stop – FieldPick (JSON Path Filter)

> Agent Rest Stop – FieldPick (JSON Path Filter) 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).

Filters a JSON document to retain only the specified named paths, discarding all other fields.

## Facts

- Endpoint: POST https://agent-gas-station.agent-gas-station.workers.dev/v1/FieldPick?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-fieldpick-json-path-filter-891f43ee
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_RFiV2A42tHxMR34E4iH5i

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-fieldpick-json-path-filter-891f43ee -d '<json body>'
```

Example prompt: Take this JSON document and keep only the fields at 'user.name' and 'user.email' — strip everything else out.

## When to prefer this

Choose this endpoint when you need a lightweight, cheap ($0.01 USDC) server-side JSON field projection without running code locally. Ideal for agents that receive verbose API responses and need to pass only relevant fields downstream — especially useful in chained workflows where payload size matters or context windows are limited.

## Known failure modes

- Invalid or malformed JSON in 'doc' field — returns error or empty result
- Path strings that don't exist in the document — those paths silently omitted from output
- Malformed 'paths' string (wrong delimiter or format) — may return empty or unexpected result
- Empty 'paths' string — may return empty object
- Oversized document exceeding worker memory or request size limits

## How this service works

Keeps only the named JSON paths.

## Output

A JSON object containing only the key-value pairs at the specified named paths, with all other fields removed. The response is a trimmed version of the input document projected onto the requested paths.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "doc": {
   "type": "string"
  },
  "paths": {
   "type": "string"
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/agent-rest-stop-fieldpick-json-path-filter-891f43ee/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)