# PennyRail AI Chat Mini – Chat Completion

> PennyRail AI Chat Mini – Chat Completion 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).

Provides a paid chat completion endpoint using a mini/small AI language model, accessible via x402 micropayment settlement at $0.02 USDC per call.

## Facts

- Endpoint: POST https://pennyrail.vercel.app/api/p/premium/ai.chat-mini--chat-completion
- 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-ai-chat-mini-chat-completion-b9205315
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_tfFIJsM67ZOOiZL20Fh32

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-ai-chat-mini-chat-completion-b9205315 -d '<json body>'
```

Example prompt: Send this message to the PennyRail mini chat model and get a response: 'Explain the difference between supervised and unsupervised learning in two sentences.' — charge the $0.02 USDC fee automatically.

## When to prefer this

Choose this endpoint when you need a cheap, per-call AI chat completion without a subscription, especially inside an autonomous agent that can pay x402 micropayments in USDC. It is best suited for lightweight inference tasks where cost-per-call matters (at $0.02) and a mini/small model is sufficient. Prefer it over full-scale LLM APIs when budget is tight or the task is simple (summarization, short Q&A, classification).

## Known failure modes

- Payment not included or insufficient USDC balance — 402 Payment Required
- Malformed input object missing required 'input' field — 400 Bad Request
- Underlying LLM provider unavailable or rate-limited — 503 or 500 error
- Empty or null input resulting in a nonsensical or error response
- USDC transaction settlement failure causing request to be rejected
- Response schema is loose (additionalProperties: true), so field names may vary across calls

## How this service works

Machine-readable settlement service

## Output

Returns a JSON object containing the AI-generated chat completion text or message in response to the provided input prompt. The response schema is open-ended (additionalProperties: true), so the reply structure may include a message body, usage stats, or model metadata depending on the underlying model.

## 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-ai-chat-mini-chat-completion-b9205315/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)