# PennyRail GPT-4o Mini Chat

> PennyRail GPT-4o Mini Chat is a paid API for AI agents from pennyrail.vercel.app, paid per call via x402, $0.02/call, status unknown (last checked 2026-09-15).

Sends a chat message to GPT-4o Mini via a paid micropayment API proxy and returns the model's response

## Facts

- Endpoint: POST https://pennyrail.vercel.app/api/p/premium/ai.chat-mini--gpt-4o-mini-chat
- Price: $0.02/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/pennyrail-gpt-4o-mini-chat-008144b4
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_rw6DYrNHfObGEAdAou24z

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-gpt-4o-mini-chat-008144b4 -d '<json body>'
```

Example prompt: Send my question 'What are the top 3 causes of the French Revolution?' to the GPT-4o Mini chat model and give me a concise answer.

## When to prefer this

Choose this endpoint when you need lightweight, cost-efficient chat completions via GPT-4o Mini at $0.02 per call without managing your own OpenAI API keys, and when your agent or application supports x402 micropayment flows. It is ideal for agentic pipelines that need pay-per-use text generation without subscription overhead.

## Known failure modes

- Payment failure: insufficient USDC balance causes 402 rejection before the model is called
- Invalid input schema: missing or malformed 'input' object returns a 400 or validation error
- Model timeout: GPT-4o Mini upstream latency occasionally causes gateway timeouts
- Opaque response schema: additionalProperties:true means response shape may vary and agents must handle unexpected fields
- Rate limiting: high-frequency callers may be throttled by the proxy

## How this service works

Machine-readable settlement service

## Output

Returns a JSON object containing the GPT-4o Mini model's text response to the provided input, structured as an open-ended object. The exact fields depend on the model output but typically include the generated message or completion.

## 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-gpt-4o-mini-chat-008144b4/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)