# x402engine Claude Opus LLM Endpoint

> x402engine Claude Opus LLM Endpoint 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).

Sends a chat conversation to Anthropic's Claude Opus model and returns a completion, billed per call via HTTP 402 micropayment in USDC

## Facts

- Endpoint: POST https://x402engine.app/api/llm/claude-opus?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/x402engine-claude-opus-llm-endpoint-0cf4a6ae
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_IzwekXSgJFju2MQXN7ti5

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-claude-opus-llm-endpoint-0cf4a6ae -d '<json body>'
```

Example prompt: Ask Claude Opus to analyze this legal document and summarize the key obligations: [document text here] — use streaming so I see the response as it comes in.

## When to prefer this

Choose this endpoint when you need Anthropic's most capable Claude Opus model for complex reasoning, nuanced writing, or difficult tool-calling tasks, and want to pay per call in USDC without managing an Anthropic API key or subscription. Prefer this over cheaper Claude Haiku/Sonnet endpoints when task quality is paramount. Use x402engine's micropayment model when your agent needs on-demand LLM access without upfront commitment.

## Known failure modes

- Payment not settled — 402 returned if USDC payment header is missing or insufficient
- Invalid messages array — 400 error if required 'messages' field is absent or malformed
- Token limit exceeded — model returns finish_reason='length' if context is too long
- Tool call format error — 400 if tool definitions do not match the required function schema
- Streaming connection drop — partial SSE response if network is interrupted mid-stream
- Rate limiting — 429 if too many concurrent calls are made

## 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 containing the assistant's message content, the model identifier (e.g. anthropic/claude-opus-4.6), choice index, and finish reason (stop, tool_calls, etc.). When streaming is enabled, returns live SSE chunks 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": {
      "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."
      },
      "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": "ar
… (truncated)
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "model": "anthropic/claude-opus-4.6",
  "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-claude-opus-llm-endpoint-0cf4a6ae/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)