# x-402 LLM Pro (Long-form Inference)

> x-402 LLM Pro (Long-form Inference) is a paid API for AI agents from api.x-402.online, paid per call via x402, $0.02/call, status unknown (last checked 2026-10-20).

Runs long-form LLM inference with up to 8000 output tokens, providing extended answers that standard LLM endpoints would truncate.

## Facts

- Endpoint: GET https://api.x-402.online/v1/llm/pro?utm_source=zero.xyz
- Price: $0.02/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-20
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/x-402-llm-pro-long-form-inference-68b8cf31
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_Jjpk22is0ovTJEivbbsxD

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 x-402-llm-pro-long-form-inference-68b8cf31
```

Example prompt: Write me a thorough 2000-word technical overview of how transformer-based language models work, covering attention mechanisms, training, and inference — I need the full detailed answer, not a summary.

## When to prefer this

Choose this endpoint when you need LLM-generated responses longer than ~2000 tokens — such as full documents, detailed reports, long essays, or complex multi-part answers — and the standard /v1/llm endpoint would truncate the output. Prefer this over the base LLM endpoint whenever completeness of the answer matters more than cost savings.

## Known failure modes

- Prompt too vague or empty — model may produce off-topic or minimal output
- max_tokens set below actual needed length — response still truncated
- Rate limiting or payment failure at $0.006 USDC per call — 402 payment required error
- Model timeout on extremely complex prompts
- Prompt injection in user-supplied content passed through to the model

## How this service works

Get a long completion with a large output budget, same engine as /v1/llm. Long-form LLM inference: same engine as /v1/llm with a four times larger output budget, up to 8000 tokens, for answers the cheap route truncates. Body: {prompt, system?, max_tokens?}

## Output

The agent receives a generated text completion from the LLM with up to 8000 output tokens, suitable for long-form content, detailed explanations, extensive documents, and thorough analyses that would be truncated by standard inference endpoints.

## 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": {
     "properties": {}
    },
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "bodyType": {
     "enum": [
      "json",
      "form-data",
      "text"
     ],
     "type": "string"
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "usage": {
   "output_tokens": 300
  },
  "output": "…"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/x-402-llm-pro-long-form-inference-68b8cf31/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.x-402.online](https://www.zero.xyz/host/api.x-402.online/llms.txt)