### Check for existing issues

- [x] I have searched the existing issues and checked that my issue is not a duplicate.

### What happened?

I had created a PR to add qwen3.6 in model_prices_and_context_window.json, but I found that tiered_pricing did't support cache_creation_input_token_cost. Test error is " Failed validating 'additionalProperties' in schema['additionalProperties']['properties']['tiered_pricing']['items']:" . It wonder why it is not supported in current verison, but i think it shuould be fixed

<img width="1706" height="392" alt="Image" src="https://github.com/user-attachments/assets/a292e98c-cc09-46b7-b02b-5701a6776f0c" />

### Steps to Reproduce

1. check the price at this url: https://openrouter.ai/qwen/qwen3.6-plus

### Relevant log output

```shell

```

### What part of LiteLLM is this about?

SDK (litellm Python package)

### What LiteLLM version are you on ?

v1.53.1

### Twitter / LinkedIn details

_No response_