# PennyRail Number Percent Change

> PennyRail Number Percent Change 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).

Computes the percent change between two numeric values, returning the operation name and result

## Facts

- Endpoint: POST https://pennyrail.vercel.app/api/f/number.percent-change
- 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-number-percent-change-f0fe92b2
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_3QHTOXqrjEozEYQM2nE3Y

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-number-percent-change-f0fe92b2 -d '<json body>'
```

Example prompt: What's the percent change from 250 to 315?

## When to prefer this

Choose this endpoint when you need a lightweight, pay-per-call computation of percent change between two numbers without setting up local math logic. Ideal for AI agents that need on-demand arithmetic in pipelines where installing a math library is impractical, or when traceability of the operation name alongside the result is useful.

## Known failure modes

- Missing 'from' or 'to' fields in the input object returns a validation error
- Division by zero if 'from' value is 0 (percent change is undefined)
- Non-numeric inputs may cause computation failure
- Payment failure via x402 protocol results in 402 response before computation occurs

## How this service works

Machine-readable settlement service

## Output

Returns a JSON object with an 'operation' string identifying the computation performed and a 'result' field containing the calculated percent change value (typically a decimal or percentage number).

## Request schema (JSON Schema)

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

## 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-number-percent-change-f0fe92b2/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)