List guardrails

{
  "guardrails": [
    {
      "allowed_models": [
        "gpt-5.4"
      ],
      "allowed_providers": [],
      "assignment_count": 1,
      "blocked_models": [],
      "blocked_providers": [],
      "created_at": "2026-07-27T10:00:00.000Z",
      "credit_limit_cents": 50000,
      "credit_limit_reset_interval": "monthly",
      "description": "Production policy",
      "enabled": true,
      "id": "guardrail_123",
      "model_budgets": [
        {
          "credit_limit_cents": 10000,
          "credit_limit_reset_interval": "monthly",
          "match_mode": "include",
          "models": [
            "gpt-5.4"
          ]
        }
      ],
      "name": "Production budget"
    }
  ],
  "pagination": {
    "limit": 20,
    "page": 1,
    "pages": 1,
    "total": 1
  }
}

{
  "error": "Authentication required"
}

{
  "error": "Management API key required"
}

{
  "error": "Account admin required"
}

{
  "error": "page must be an integer"
}