# Grok 4.5 LLM via x402engine

> Grok 4.5 LLM via x402engine is a paid API for AI agents from x402engine.app, paid per call via x402, $0.028874/call, status unknown (last checked 2026-10-19).

Send a chat completion request to xAI's Grok 4.5 model and receive a response, billed per-call via HTTP 402 micropayment in USDC

## Facts

- Endpoint: POST https://x402engine.app/api/llm/grok-4.5?utm_source=zero.xyz
- Price: $0.028874/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-19
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/grok-4-5-llm-via-x402engine-2d83bfa2
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_AiM4zGexT1MmCq36B_FA7

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 grok-4-5-llm-via-x402engine-2d83bfa2 -d '<json body>'
```

Example prompt: Ask Grok 4.5 to write a concise explanation of quantum entanglement for a high school audience — I want to pay per call with USDC rather than committing to a subscription.

## When to prefer this

Choose this endpoint when you need Grok 4.5 specifically — known for strong reasoning and coding — without a monthly xAI subscription, paying only per call in USDC on Base, Solana, or MegaETH. Prefer over self-hosted or subscription alternatives when running sporadic or low-volume workloads, or when your agent stack already handles x402 HTTP payments and you want access to 87+ LLMs through one unified interface.

## Known failure modes

- 402 Payment Required if wallet has insufficient USDC balance
- 400 Bad Request if messages array is missing or malformed
- Model capability mismatch if requesting unsupported features (check /docs/llm-capabilities.md)
- Streaming connection drop if payment settlement is delayed
- Tool call schema errors if function definitions are malformed
- Timeout on very long prompts or high top_p sampling

## How this service works

x402engine — xAI's latest multimodal model with 500k context and strong tool use

## Output

Returns an OpenAI-compatible JSON object containing a choices array with the assistant's message (role, content), finish_reason (e.g. 'stop'), and the model name ('x-ai/grok-4.5'). When streaming is enabled, returns Server-Sent Events in OpenAI SSE format. Tool calls are returned in the message when the model invokes a function.

## 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."
      },
      "logprobs": {
       "type": "boolean",
       "description": "Model-supported logprobs; see /docs/llm-capabilities.md."
      },
      "messages": {
       "type": "array",
       "items": {
        "type": "object",
        "anyOf": [
         {
          "required": [
           "content"
          ]
         },
         {
          "
… (truncated)
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "model": "x-ai/grok-4.5",
  "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/grok-4-5-llm-via-x402engine-2d83bfa2/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)