# x402engine Gemini 3.1 Flash Lite LLM

> x402engine Gemini 3.1 Flash Lite LLM is a paid API for AI agents from x402engine.app, paid per call via x402, $0.00486/call, status unknown (last checked 2026-10-20).

Call Google's Gemini 3.1 Flash Lite model via pay-per-call HTTP 402 micropayment, with full OpenAI-compatible chat messaging, tool use, streaming, and multimodal input support.

## Facts

- Endpoint: POST https://x402engine.app/api/llm/gemini-3.1-flash-lite?utm_source=zero.xyz
- Price: $0.00486/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-20
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/x402engine-gemini-3-1-flash-lite-llm-f35923b2
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_LWT7ci-T7MOlVTZZTQue2

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-3-1-flash-lite-llm-f35923b2 -d '<json body>'
```

Example prompt: Send a chat message to Gemini 3.1 Flash Lite asking it to summarize the following document and return the response — use streaming and set top_p to 0.9: [document text here].

## When to prefer this

Choose this endpoint when you need a fast, cheap LLM call without managing API keys or subscriptions — ideal for AI agents that need pay-per-call economics via USDC micropayments. Prefer Gemini 3.1 Flash Lite specifically for low-latency, cost-sensitive inference tasks where a capable but lightweight Google model is sufficient. Best when you want OpenAI-compatible chat format with optional tool calling, streaming, or multimodal inputs, billed atomically per call on Base, MegaETH, or Solana.

## Known failure modes

- Payment failure or insufficient USDC balance — 402 response with payment required details
- Invalid messages array or missing required 'role' field — 400 validation error
- Model context window exceeded with large message arrays — truncation or error
- Tool call schema mismatch causing function dispatch failure
- Streaming connection dropped before completion — partial SSE response
- Unsupported content type in multimodal input — 400 or ignored field

## How this service works

x402engine — Google's fastest and cheapest model — ideal for high-volume, low-latency tasks

## Output

Returns an OpenAI-compatible JSON object with a choices array containing the assistant message (role, content, tool_calls if applicable), finish_reason, and model name. When streaming is enabled, returns live SSE events after payment settles. Content field is also returned at top level for convenience.

## 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."
      },
      "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": "array",
       "items": {
        "type": "object",
        "anyOf": [
         {
          "required": [
           "content"
          ]
         },
         {
          "required": [
           "tool_calls"
          ]
         }
        ],
        "required": [
         "role"
        ],
        "propert
… (truncated)
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "model": "google/gemini-3.1-flash-lite-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-3-1-flash-lite-llm-f35923b2/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)