I have dug a bit deeper on this these properties are supported but not as top level request body fields, instead they are available in object element fields under `rate_limits`. The actual payload looks like::

```
{
    "guardrails": { /* ... */ },
    "inference_table_config": { /* ... */ },
    "rate_limits": [
      {
        "renewal_period": "MINUTE|HOUR|DAY",
        "calls": 100,
        "tokens": 1000,           // ← tokens supported HERE (in rate_limits)
        "principal": "user@company.com", // ← principals supported HERE  
        "key": "USER|ENDPOINT"
      }
    ],
    "usage_tracking_config": { /* ... */ },
    "fallback_config": { /* ... */ }
  }
```

For example to update the config for an ai-gateway resource you would use:

```
curl -X PUT \
  "https://<deployment url>/api/2.0/serving-endpoints/{name}/ai-gateway" \
  -H "Authorization: Bearer <token>" \
  -H "Content-Type: application/json" \
  -d '{
    "rate_limits": [
      {
        "renewal_period": "HOUR",
        "calls": 100,
        "tokens": 1000,
        "principal": "user@company.com"
      }
    ]
  }'
```

Let me know how this goes