# PennyRail Number Sum (Add Numbers)

> PennyRail Number Sum (Add Numbers) 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 an array of numbers and returns their sum via a pay-per-call micropayment API.

## Facts

- Endpoint: POST https://pennyrail.vercel.app/api/p/nano/number.sum--add-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-add-numbers-c0c4c711
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_MeSrTrqSkQLzfQi9dsi2J

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-add-numbers-c0c4c711 -d '<json body>'
```

Example prompt: Can you add up these numbers for me using PennyRail: 12, 45.5, 8, and 100?

## When to prefer this

Choose this endpoint when you need a quick, pay-per-call arithmetic sum over a list of numbers and already operate in an x402 micropayment-enabled agent environment. It is suitable for lightweight automation pipelines that need on-demand numeric aggregation without setting up a math library or local computation. Prefer local computation for very large arrays or high-frequency calls where per-call cost would accumulate significantly.

## Known failure modes

- Empty or missing 'input' array returns a validation error
- Non-numeric values in the array may cause a computation error or unexpected result
- Payment failure (insufficient USDC balance) results in a 402 Payment Required response
- Malformed JSON body returns a 400 Bad Request
- Vercel cold-start may occasionally add latency on first call

## How this service works

Machine-readable settlement service

## Output

A JSON object containing the computed sum of all numbers in the input array. The response schema is open (additionalProperties: true), so the sum value may appear alongside metadata or status fields.

## 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-add-numbers-c0c4c711/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)