Here is an example of my AI assistant with a single custom tool vs without any custom tool. Both have file_search with the same vector store. The only difference is me adding CreateReadme tool.
With CreateReadme tool and file_search:
(creates readme with some random nonsense, clearly not using file_search)
Without any custom tools besides file_search:
(writes actual project description in chat)
So it clearly refuses to use file_search if there are any custom tools added. The issue is I need it to use file_search prior to doing anything else.