# PennyRail JSON Pick – Select Object Keys

> PennyRail JSON Pick – Select Object Keys is a paid API for AI agents from pennyrail.vercel.app, paid per call via x402, $0.001/call, status unknown (last checked 2026-09-14).

Accepts a JSON object and returns a new object containing only the specified subset of keys (pick/select operation)

## Facts

- Endpoint: POST https://pennyrail.vercel.app/api/p/nano/json.pick--select-object-keys
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/pennyrail-json-pick-select-object-keys-d04c8173
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_HNyDIvVrpN95hYG4Xown1

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-pick-select-object-keys-d04c8173 -d '<json body>'
```

Example prompt: I have a JSON object with lots of fields — can you pick just the 'name', 'email', and 'role' keys from it and give me back a clean object with only those three?

## When to prefer this

Use this endpoint when you need a lightweight, paid micro-service to programmatically project a subset of keys from a JSON object — especially in agent pipelines where you want a deterministic, stateless transformation without running custom code. Prefer this over general-purpose code execution when you want a simple, auditable pick operation with a clear x402 payment trail at $0.001 per call.

## Known failure modes

- Missing 'input' field in request body returns a validation error
- If requested keys do not exist on the input object, those keys are silently omitted from the result
- Malformed JSON body causes a parse error
- Payment failure or insufficient USDC balance blocks the request via x402 payment protocol
- Empty key selection may return an empty object

## How this service works

Machine-readable settlement service

## Output

Returns a new JSON object containing only the key-value pairs from the input object whose keys were specified in the selection. All other keys from the input are omitted. The response is a plain JSON object with the picked fields.

## Request schema (JSON Schema)

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

## Response schema (JSON Schema)

```json
{
 "type": "object",
 "additionalProperties": true
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/pennyrail-json-pick-select-object-keys-d04c8173/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)