# PennyRail Number Sum

> PennyRail Number Sum 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 sum (total) of an array of numbers via a paid API endpoint

## Facts

- Endpoint: POST https://pennyrail.vercel.app/api/p/nano/number.sum--total-numbers
- 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-sum-cc9b119c
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_urR7u99RD7uiG60r2kSfu

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-sum-cc9b119c -d '<json body>'
```

Example prompt: Add up all the numbers in this list for me: [4, 17, 8, 23, 5] and give me the total.

## When to prefer this

Use this endpoint when you need a simple, pay-per-call arithmetic sum of an array of numbers without hosting your own compute. It is particularly useful in agent workflows where you want a lightweight, on-demand computation step with a predictable micro-payment cost, rather than running local code or spinning up a full computation service.

## Known failure modes

- Empty or missing input array returns an error
- Non-numeric values in the array may cause computation failure or be ignored
- Payment failure (402) if USDC balance is insufficient
- Malformed request body (missing 'input' key) returns a validation error
- Very large arrays may hit request size or timeout limits

## How this service works

Machine-readable settlement service

## Output

Returns a JSON object containing the computed sum (total) of all numbers provided in the input array. The response schema is open-ended, likely including a field for the total or sum value.

## Request schema (JSON Schema)

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

## Response schema (JSON Schema)

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

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/pennyrail-number-sum-cc9b119c/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)