# agent402.tools LLM Pro Inference (GPT-4o / GPT-4.1)

> agent402.tools LLM Pro Inference (GPT-4o / GPT-4.1) is a paid API for AI agents from agent402.tools, paid per call via x402, $0.1/call, status healthy (last checked 2026-10-10, last successful call 2026-09-29).

Proxies LLM inference requests to GPT-4o or GPT-4.1 with vision and structured output support, paid per-call via x402 with no API key required.

## Facts

- Endpoint: POST https://agent402.tools/api/llm-pro?utm_source=zero.xyz
- Price: $0.1/call
- Payment: x402
- Status: healthy
- Last checked: 2026-10-10
- Last successful call: 2026-09-29
- Success rate: 100% of calls made through Zero
- Rating: 4.5 / 5 from 2 reviews
- Activations on Zero: 40
- Tags: x402
- Canonical page: https://www.zero.xyz/c/agent402-tools-llm-pro-inference-gpt-4o-gpt-4-1-aa38c191
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_TXGRINeNg_RwthnUvuPty

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 agent402-tools-llm-pro-inference-gpt-4o-gpt-4-1-aa38c191 -d '<json body>'
```

Example prompt: Send this conversation to GPT-4o with temperature 0.7 and give me the response as a JSON object matching my schema: system says 'you are a data extractor', user says 'extract the company name and revenue from: Acme Corp reported $4.2M in revenue last quarter'.

## When to prefer this

Choose this endpoint when you need GPT-4o or GPT-4.1 capabilities without managing an OpenAI API key or subscription, want pay-per-call billing in USDC via x402, need vision support for up to 2 image URLs, or require structured JSON output with response_format. Ideal for agent workflows that need occasional high-quality LLM calls billed transparently per invocation.

## Known failure modes

- Input exceeds 16k character limit — request rejected
- max_tokens above 2048 — capped or rejected
- More than 2 image URLs provided — error or truncation
- Invalid model ID (not gpt-4o or gpt-4.1) — 400 error
- x402 payment failure or insufficient USDC balance — 402 payment required
- Malformed messages array format — 400 validation error
- Invalid response_format schema — structured output fails

## How this service works

LLM inference proxy (Pro tier) - GPT-4o or GPT-4.1. Supports vision (up to 2 image URLs) and structured output (response_format: json_object or json_schema). No API key needed; pay per call via x402. Input capped at 16k chars, output at 2048 tokens.

## Output

Returns the model's completion text or a structured JSON object (if response_format is specified), including the generated content up to max_tokens (default 1024, cap 2048). The response follows standard OpenAI chat completion structure.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "stop": {
   "type": "string",
   "description": "Stop sequence(s)"
  },
  "model": {
   "type": "string",
   "description": "Model ID - gpt-4o or gpt-4.1"
  },
  "top_p": {
   "type": "number",
   "description": "Nucleus sampling (0-1)"
  },
  "messages": {
   "type": "array",
   "description": "Array of {role, content} objects. content can be a string or array of {type:'text',text} and {type:'image_url',image_url:{url,detail}} blocks"
  },
  "max_tokens": {
   "type": "number",
   "description": "Max output tokens (default 1024, cap 2048)"
  },
  "temperature": {
   "type": "number",
   "description": "Sampling temperature (0-2)"
  },
  "response_format": {
   "type": "object",
   "description": "Optional: {type:\"json_object\"} or {type:\"json_schema\",json_schema:{name,schema}}"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "model": "gpt-4o",
  "usage": {
   "total_tokens": 20,
   "prompt_tokens": 12,
   "completion_tokens": 8
  },
  "choices": [
   {
    "message": {
     "role": "assistant",
     "content": "Hello! How can I help you today?"
    },
    "finish_reason": "stop"
   }
  ],
  "provider": "openai"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/agent402-tools-llm-pro-inference-gpt-4o-gpt-4-1-aa38c191/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from agent402.tools](https://www.zero.xyz/host/agent402.tools/llms.txt)