# x402-services Chat Pro — Multi-Model Frontier AI Completion

> x402-services Chat Pro — Multi-Model Frontier AI Completion is a paid API for AI agents from x402-services-production.up.railway.app, paid per call via x402, $0.03/call, status unknown (last checked 2026-09-15).

Pay-per-call frontier LLM chat completions (GPT-4o, Claude Sonnet 4, Gemini 2.5 Pro, DeepSeek R1, Grok 3) via OpenAI-compatible messages, payable in USDG or USDC

## Facts

- Endpoint: POST https://x402-services-production.up.railway.app/api/ai/chat-pro
- Price: $0.03/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/x402-services-chat-pro-multi-model-frontier-ai-completion-ec0f50dc
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_I9hyb7_0h0aFkpuL7ulaN

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 x402-services-chat-pro-multi-model-frontier-ai-completion-ec0f50dc -d '<json body>'
```

Example prompt: Ask GPT-4o to write a concise executive summary of the following meeting notes — pay per call in USDC: [paste notes here].

## When to prefer this

Choose this endpoint when you need pay-per-call access to frontier models (GPT-4o, Claude Sonnet 4, Gemini 2.5 Pro, DeepSeek R1, Grok 3) without committing to a monthly subscription, especially when paying in USDC or USDG on-chain. Ideal for AI agents that need occasional high-quality reasoning, drafting, or summarization at $0.03 per call. Best when input fits within 6k chars and a concise 800-token response is sufficient. Prefer over direct provider APIs when stablecoin payment and a unified multi-model interface matter.

## Known failure modes

- Input exceeds 6,000 character limit — request rejected
- Model name not recognized or unavailable — returns error
- Insufficient USDC/USDG payment — 402 Payment Required response
- Output truncated at 800 token cap — partial answers for long tasks
- Network timeout if upstream model provider is slow
- Invalid messages array format — schema validation error

## How this service works

Frontier-model chat completion via x402 (gpt-4o, claude-sonnet-4, gemini-2.5-pro, deepseek-r1, grok-3). OpenAI-compatible messages. Payable in USDG on Robinhood Chain or USDC anywhere. Caps: 6k chars in / 800 tokens out.

## Output

Returns an assistant message containing the frontier model's text response. The response is limited to 800 output tokens. The specific model used determines reasoning depth and style. The response follows OpenAI-compatible chat completion format.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method",
    "bodyType",
    "body"
   ],
   "properties": {
    "body": {
     "type": "object"
    },
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "POST"
     ],
     "type": "string"
    },
    "bodyType": {
     "enum": [
      "json"
     ],
     "type": "string"
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/x402-services-chat-pro-multi-model-frontier-ai-completion-ec0f50dc/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from x402-services-production.up.railway.app](https://www.zero.xyz/host/x402-services-production.up.railway.app/llms.txt)