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PennyRail JSON Key Picker
x402
PennyRail JSON Key Picker 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 a specified subset of keys from a JSON object, returning only the requested fields
Price / call$0.001
Success—
StatusUnknown
How this service works
Machine-readable settlement service
Output
Returns an object containing an 'operation' string describing what was performed, and a 'result' field containing the new JSON object with only the requested keys present. Additional metadata fields may also be included.
Example use cases
Trim API response before storing
“I got a huge user object back from an API but I only need 'userId', 'displayName', and 'avatarUrl' — can you extract just those three fields from the JSON for me?”
Sanitize data before logging
“Strip this event payload down to only the 'eventType', 'timestamp', and 'sessionId' keys before we log it — I don't want PII in the logs.”
Prepare partial payload for downstream service
“From this product record, pull out only 'sku', 'price', and 'stock' — that's all the inventory service needs, leave everything else out.”
Technical details
Endpoint
POSThttps://pennyrail.vercel.app/api/f/json.pickWhen to prefer
Use this endpoint when you need a lightweight, pay-per-call service to programmatically project a specific set of keys from a JSON object without writing custom transformation logic. It is well-suited for agent pipelines that need to sanitize, slim down, or reshape JSON payloads on the fly with minimal overhead.
Side effects
- Missing 'input' field in request body returns a validation error
- Requesting keys that do not exist in the source object may return empty or partial results
- Malformed JSON in the input value may cause a parsing error
- Payment failure (402) if USDC balance is insufficient or x402 header is missing
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | {value,keys:string[]} |
Output
Schema · Response
| Field | Type | Description |
|---|---|---|
| resultrequired | — | |
| operationrequired | string |
Tags
x402
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