List available model presets

{
  "object": "list",
  "data": [
    {
      "tier": "economy",
      "description": "string",
      "generation": {
        "provider": "anthropic",
        "model": "string"
      },
      "assessment": {
        "provider": "anthropic",
        "model": "string"
      }
    }
  ],
  "default_tier": "economy"
}