How do you pass a system prompt in the Claude API?

JSON Payload Configuration

{
  "model": "claude-3-5-sonnet-20241022",
  "max_tokens": 1024,
  "system": "You are a specialized code translator. Output only clean code.",
  "messages": [
    {"role": "user", "content": "Translate x = 1 to JavaScript."}
  ]
}