I have ran into a few issues while learning how to use Custom Agents in Databricks Apps that I would like to call out - both to help others and hopefully motivate platform improvements.

1. The only model that seems to work is databricks-meta-llama-3-3-70b-instruct, but I only found that out through a DataExpert.io YouTube video. It would be nice if the app templates would default to this or at least provide some guidance on the Free Edition limitations page. 
2. Recent changes to MCP have caused issues with the default OpenAI Agents SDK app template. You have to manually add "mcp<2.0.0" to the dependencies in pyproject.toml to get it up and running. 
3. The second message from the user starts to cause errors. I haven't figured out how to solve this, but it is something related to the format of the message chain. For example:

{
  "detail": "Unhandled item type or structure: {'status': None, 'content': [{'text': \"Hello, it's nice to meet you. Is there something I can help you with or would you like to chat?\", 'type': 'output_text'}], 'role': 'assistant', 'type': 'message'}"
}​