Recommended way to handle files not directly supported by Gemini #1751

Currently I have a requirement to be able to read .xlsx files. However this is not supported by Gemini so if I follow the usual workflow either by passing in as an artifact or directly in prompt, ADK errors out.
https://ai.google.dev/gemini-api/docs/document-processing?lang=python#technical-details

The workaround is that I create tools to be able to read excel files and pass it back to the agent, however the issue is that this workaround doesn't quite work on adk web. I have to separate out file handling from the Agent.

What is the recommended way to tackle this issue? I want to be able to both use it as a workflow from the command line as well as in adk web.