# x402engine Claude Opus 4.8 LLM API

> x402engine Claude Opus 4.8 LLM API 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).

Call Anthropic's Claude Opus 4.8 model via a pay-per-call HTTP 402 micropayment endpoint, returning OpenAI-compatible chat completions

## Facts

- Endpoint: POST https://x402engine.app/api/llm/claude-opus-4.8?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-4-8-llm-api-2ebb35e4
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_nzVhwH6vO8Fp2Hn3ZGxcH

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-4-8-llm-api-2ebb35e4 -d '<json body>'
```

Example prompt: Ask Claude Opus 4.8 to write a detailed technical explanation of how transformer attention works, and stream the response back — pay with USDC on Base via x402.

## When to prefer this

Choose this endpoint when you need Anthropic's Claude Opus 4.8 specifically — one of the highest-capability frontier models — without provisioning an Anthropic API key or managing billing accounts. Ideal for agents that need pay-per-call crypto micropayments (USDC on Base/Solana or USDm on MegaETH), support OpenAI-compatible message formats, and want tool/function calling, streaming, image input, or PDF parsing in a single endpoint. Prefer over generic OpenAI-compatible proxies when Claude's reasoning style or constitutional training is important to the task.

## Known failure modes

- 402 Payment Required if USDC balance is insufficient or payment settlement fails
- 400 Bad Request if the messages array is missing or malformed
- 413 if content exceeds model context window
- Streaming may be interrupted if network drops after payment settlement
- Tool call format errors if function definitions do not conform to OpenAI function schema
- Model unavailability or upstream Anthropic outage returns 5xx

## 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 model name ('anthropic/claude-opus-4.8'), a choices array with the assistant message (role, content, finish_reason), and optionally streamed SSE chunks if stream=true. Tool call arrays are included when the model invokes client-defined functions.

## 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."
      },
      "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
… (truncated)
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "model": "anthropic/claude-opus-4.8",
  "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-4-8-llm-api-2ebb35e4/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)