fix: apply cache control correctly to tools

[yingjiehe-xyz]

fix #1066

Test:

Enable tools and see higher cache_discount

{
  "data": {
    "id": "gen-1738712804-5wvhsREvgvXR99HBpioS",
    "upstream_id": "msg_01GQ8Vs5vVjo3C5viSgEYjsm",
    "total_cost": 0.0028803,
    "cache_discount": 0.0042687,
    "provider_name": "Anthropic",
    "created_at": "2025-02-04T23:46:48.29004+00:00",
    "model": "anthropic/claude-3.5-sonnet",
    "app_id": 1784029,
    "streamed": true,
    "cancelled": false,
    "latency": 1191,
    "moderation_latency": 205,
    "generation_time": 1780,
    "tokens_prompt": 1099,
    "tokens_completion": 103,
    "native_tokens_prompt": 1758,
    "native_tokens_completion": 125,
    "native_tokens_reasoning": 0,
    "is_byok": false,
    "finish_reason": "stop",
    "native_finish_reason": "stop",
    "usage": 0.0028803
  }
}