Keeping model information up to date with open router

[AkshatGiri]

I'm using litellm with openrouter so it's easy to switch between different models. I noticed that there is a json file model_prices_and_context_window_backup.json file that contains information about the model context size and pricing, however information for several models ( especially openrouter ones ) is out of date. Some models are missing out right.

Missing eg - Llama 3.1 8b instruct ( created a pr to add it to the json #7725 )
Out of date eg - Mistral 7b instruct ( the context size is listed at 8k which is correct for the free version, however the paid one is 32k token context size ).

Although this information doesn't affect the api calls, I think it's is important especially when trying to make sure that the inputs don't run over the models context limit. I think we should try to keep it fairly accurate.

Openrouter has an api that lists all the models and information about them.

Here's the link - https://openrouter.ai/api/v1/models

For my script I've added the following code to update all the open router models automatically at the beginning of the script.

from litellm import model_cost

def fetch_openrouter_models():
  url = "https://openrouter.ai/api/v1/models"
  response = requests.get(url)
  return response.json()

def openrouter_model_to_litellm(model):
  return { 
    "max_tokens": model['context_length'],
    "input_cost_per_token": float(model['pricing']['prompt']),
    "output_cost_per_token": float(model['pricing']['completion']),
    "litellm_provider": "openrouter",
    "mode": "chat"
  }  

models = fetch_openrouter_models()['data']

for model in models:
  model_cost[f'openrouter/{model['id']}'] = openrouter_model_to_litellm(model)

I also did notice that litellm has a way to load custom json files for model information perhaps and it might be making a api call to get the latest models from the proxy server anyways ( didn't look too deep yet ).

I'd be happy to propose a few solutions and create prs to potentially make this better if yall are down.