Track LLM Usage and Cost in Google Sheets

## 4. Use Custom LLM Subnode to Track Usage & Cost [Learn more about the Langchain Code Node]({{ $env.WEBHOOK_URL }} By creating our custom LLM subnode using the Langchain Code node, we are able to tap into the chat completion's response which contains the token usage metadata for the information extractor request. With this, we can calculate exactly how much the client's request is costing per use! The only remaining step then is to store this data somewhere. Rather than importing more dependencies or hardcoding more credentials, a novel solution can be to attach a tool to our subnode. Here, we've decided to use the Google Sheets tool and append the client's usage metrics to the sheet. Check it out here - [Client Usage Log]( {{ $env.WEBHOOK_URL }}