# Claude Opus 4.5 via x402engine (Pay-per-call)

> Claude Opus 4.5 via x402engine (Pay-per-call) is a paid API for AI agents from x402engine.app, paid per call via x402, $0.070034/call, status unknown (last checked 2026-10-12).

Runs inference on Anthropic's Claude Opus 4.5 model via a pay-per-call HTTP 402 micropayment API, returning OpenAI-compatible chat completions.

## Facts

- Endpoint: POST https://x402engine.app/api/llm/claude-opus-4.5?utm_source=zero.xyz
- Price: $0.070034/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-12
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/claude-opus-4-5-via-x402engine-pay-per-call-de748e3e
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_ZIK7_hwQGk0ayuuQiFTJ-

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 claude-opus-4-5-via-x402engine-pay-per-call-de748e3e -d '<json body>'
```

Example prompt: Using Claude Opus 4.5, help me analyze this legal contract and identify any unusual liability clauses — stream the response back as it comes in and pay the $0.07 per call fee with USDC on Base.

## When to prefer this

Choose this endpoint when you need Claude Opus 4.5 specifically — Anthropic's most capable model — without committing to a monthly Anthropic API subscription. Ideal for AI agents that pay per inference using USDC on Base, USDm on MegaETH, or USDC on Solana. Prefer over other LLM endpoints when the task demands Claude's advanced reasoning, long context, or nuanced instruction-following, and when you want OpenAI-compatible chat completion format with optional function/tool calling and streaming.

## Known failure modes

- 402 Payment Required if no valid x402 payment header is provided or USDC balance is insufficient
- 400 Bad Request if the messages array is missing or malformed
- 413 if message array exceeds token limits for Claude Opus 4.5
- Tool call schema errors if function definitions do not match the required format
- Stream interruption if connection drops before SSE completes
- Timeout on very long completions if the client does not support streaming

## 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

Returns an OpenAI-compatible JSON object with a choices array containing the assistant message, finish_reason ('stop', 'tool_calls', etc.), and the model name ('anthropic/claude-opus-4.5'). When streaming is enabled, delivers server-sent events (SSE) in real time after payment settlement.

## 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": {
      "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_k": {
       "type": "integer",
       "description": "Model-supported top_k; 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"
    
… (truncated)
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "model": "anthropic/claude-opus-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/claude-opus-4-5-via-x402engine-pay-per-call-de748e3e/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)