LLM Inference

Paid OpenAI-compatible chat completions API at https://inference.surf.cascade.fyi. Costs $0.001-$0.003 USDC per call via x402 on Solana. Use the x_payment tool for all requests.

Endpoint

Chat Completions

Generate a chat completion from a supported model.

x_payment({
  "url": "https://inference.surf.cascade.fyi/v1/chat/completions",
  "method": "POST",
  "body": "{\"model\": \"moonshotai/kimi-k2.5\", \"messages\": [{\"role\": \"user\", \"content\": \"Explain x402 in one sentence\"}]}"
})

Body Parameters:

| Param | Type | Required | Description | |-------|------|----------|-------------| | model | string | yes | Model ID (see table below) | | messages | array | yes | Array of {role, content} objects | | max_tokens | integer | no | Maximum tokens to generate | | temperature | number | no | Sampling temperature (0-2) | | top_p | number | no | Nucleus sampling (0-1) |

Message roles: system, user, assistant

Models & Pricing

| Model | Cost/call | Best for | |-------|-----------|----------| | moonshotai/kimi-k2.5 | $0.003 | High-quality output, large context (262K) | | minimax/minimax-m2.5 | $0.002 | Balanced quality/cost |

Usage Patterns

Simple question

x_payment({
  "url": "https://inference.surf.cascade.fyi/v1/chat/completions",
  "method": "POST",
  "body": "{\"model\": \"moonshotai/kimi-k2.5\", \"messages\": [{\"role\": \"user\", \"content\": \"What is the x402 protocol?\"}]}"
})

With system prompt and parameters

x_payment({
  "url": "https://inference.surf.cascade.fyi/v1/chat/completions",
  "method": "POST",
  "body": "{\"model\": \"moonshotai/kimi-k2.5\", \"messages\": [{\"role\": \"system\", \"content\": \"You are a concise technical writer.\"}, {\"role\": \"user\", \"content\": \"Write a summary of Solana's transaction model\"}], \"max_tokens\": 500, \"temperature\": 0.7}"
})

Response Format

Standard OpenAI chat completion response:

{
  "id": "gen-...",
  "object": "chat.completion",
  "model": "moonshotai/kimi-k2.5",
  "choices": [{
    "index": 0,
    "message": { "role": "assistant", "content": "..." },
    "finish_reason": "stop"
  }],
  "usage": {
    "prompt_tokens": 12,
    "completion_tokens": 42,
    "total_tokens": 54
  }
}

Errors

| HTTP | Meaning | |------|---------| | 400 | Invalid request (check model name and messages format) | | 402 | Payment required (handled automatically by x_payment) | | 502 | Upstream provider error |

Cost

Flat rate per model per call. Price is determined by the model field in the request body. Each call is independent - no sessions or state.