# x402engine Gemini 3 Pro LLM API

> x402engine Gemini 3 Pro LLM API is a paid API for AI agents from x402engine.app, paid per call via x402, $0.028883/call, status unknown (last checked 2026-10-12).

Calls Google Gemini 3 Pro via a pay-per-call HTTP 402 micropayment endpoint, returning an OpenAI-compatible chat completion response

## Facts

- Endpoint: POST https://x402engine.app/api/llm/gemini-3-pro?utm_source=zero.xyz
- Price: $0.028883/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-12
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/x402engine-gemini-3-pro-llm-api-46e8b2bc
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_XnhXndkf3xJ9FoO_NcSN_

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 x402engine-gemini-3-pro-llm-api-46e8b2bc -d '<json body>'
```

Example prompt: Ask Gemini 3 Pro to read the attached PDF research paper and write a concise executive summary highlighting the key findings, methodology, and limitations — stream the response as it comes in.

## When to prefer this

Choose this endpoint when you specifically need Google Gemini 3 Pro's capabilities (large context window, multimodal input including PDFs, images, and video, strong reasoning) and want to pay per-call via crypto micropayment without managing an API key subscription. Prefer over OpenAI or Anthropic endpoints when the task benefits from Gemini's native file-parsing plugin or when cost-per-call billing via USDC on Base/Solana or USDm on MegaETH is preferred over subscription pricing.

## Known failure modes

- Payment not settled — 402 returned if USDC/USDm balance is insufficient or payment header is missing
- Invalid messages array — 422 if required 'messages' field is absent or malformed
- Unsupported capability — model may not support all optional fields (seed, stop, top_p); check /docs/llm-capabilities.md
- Context length exceeded — error if the combined message tokens exceed Gemini 3 Pro's context window
- Streaming timeout — long responses may time out if network is unstable during SSE stream
- Rate limit — x402engine may throttle excessive requests from a single wallet

## How this service works

125 production APIs behind HTTP 402 micropayments. 87 LLMs, Kling V3 and Hailuo video generation, image generation, code execution, travel search, web scraping, TTS, and transaction simulation. Pay with USDC on Base, USDm on MegaETH, or USDC on Solana.

## Output

An OpenAI-compatible JSON object containing the model name ('google/gemini-3.1-pro-preview'), a choices array with the assistant message (role, content, finish_reason), and a top-level 'content' shortcut field. When streaming is enabled, returns SSE events in OpenAI 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",
    "bodyType",
    "body",
    "method"
   ],
   "properties": {
    "body": {
     "type": "object",
     "required": [
      "messages"
     ],
     "properties": {
      "seed": {
       "type": "integer",
       "description": "Model-supported seed; see /docs/llm-capabilities.md."
      },
      "stop": {
       "oneOf": [
        {
         "type": "string"
        },
        {
         "type": "array",
         "items": {
          "type": "string"
         },
         "maxItems": 4
        }
       ],
       "description": "Model-supported stop; see /docs/llm-capabilities.md."
      },
      "tools": {
       "type": "array",
       "items": {
        "type": "object",
        "required": [
         "function"
        ],
        "properties": {
         "type": {
          "enum": [
           "function"
          ],
          "type": "string"
         },
         "function": {
          "type": "object",
          "properties": {
           "name": {
            "type": "string"
           },
           "strict": {
            "type": "boolean"
           },
           "parameters": {
            "type": "object"
           },
           "description": {
            "type": "string"
           }
          }
         }
        }
       },
       "description": "Client-executed function definitions; return results using role=tool and tool_call_id."
      },
      "top_p": {
       "type": "number",
       "description": "Model-supported top_p; see /docs/llm-capabilities.md."
      },
      "stream": {
       "type": "boolean",
       "description": "Return live OpenAI-compatible SSE after payment settlement."
      },
      "plugins": {
       "type": "array",
       "items": {
        "type": "object",
        "required": [
         "pdf"
        ],
        "properties": {
         "id": {
          "enum": [
           "file-parser"
          ],
          "type": "string"
         },
         "pdf": {
          "type": "object",
          "properties": {
           "engine": {
            "enum": [
             "native"
            ],
            "type": "string"
           }
          }
         }
        }
       },
       "description": "Optional native PDF parser only; automatically enabled for file inputs."
      },
      "messages": {
       "type": "arra
… (truncated)
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "model": "google/gemini-3.1-pro-preview",
  "choices": [
   {
    "index": 0,
    "message": {
     "role": "assistant",
     "content": "Hello!"
    },
    "finish_reason": "stop"
   }
  ],
  "content": "Hello!"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/x402engine-gemini-3-pro-llm-api-46e8b2bc/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from x402engine.app](https://www.zero.xyz/host/x402engine.app/llms.txt)