# PennyRail JSON Keys Extractor

> PennyRail JSON Keys Extractor is a paid API for AI agents from pennyrail.vercel.app, paid per call via x402, $0.001/call, status unknown (last checked 2026-09-15).

Extracts the top-level keys from a JSON object, returning them as an array via a paid micro-transaction API

## Facts

- Endpoint: POST https://pennyrail.vercel.app/api/f/json.keys
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/pennyrail-json-keys-extractor-90e3868a
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_bGxACj1mZTuxQI2u0n9_Q

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 pennyrail-json-keys-extractor-90e3868a -d '<json body>'
```

Example prompt: Can you pull out all the top-level keys from this JSON object for me: {"name": "Alice", "age": 30, "city": "New York"}?

## When to prefer this

Use this endpoint when you need a lightweight, pay-per-call micro-service to programmatically extract the top-level keys of a JSON object without running local code. It is well-suited for agent workflows that operate in sandboxed environments where executing arbitrary JavaScript or Python is not possible, and where a simple key enumeration is needed as part of a larger data-inspection pipeline.

## Known failure modes

- Input is not a valid JSON object (e.g. array or scalar) — may return an error or empty result
- Missing required 'input' field in the request body — returns a validation error
- Payment of 0.001 USDC not completed — returns HTTP 402 Payment Required
- Network or server error on the Vercel deployment — returns 5xx response

## How this service works

Machine-readable settlement service

## Output

Returns a JSON object containing an 'operation' string indicating what was performed (e.g. 'json.keys') and a 'result' field containing the list of top-level key names extracted from the input JSON object.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "description": "JSON value"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "object",
 "required": [
  "operation",
  "result"
 ],
 "properties": {
  "result": {},
  "operation": {
   "type": "string"
  }
 },
 "additionalProperties": true
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/pennyrail-json-keys-extractor-90e3868a/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from pennyrail.vercel.app](https://www.zero.xyz/host/pennyrail.vercel.app/llms.txt)