Structured Output with /generate API and tools

I'm trying to use the /generate API with an

output

output

property in the POST body where I define Json Schema.

This doesn't seem to call any of my tools.

The docs note the use of

experimental_output

experimental_output

why when I try and use this instead it errors with

Function calling with a response mime type: application/json is unsupported

Function calling with a response mime type: application/json is unsupported

How can I use /generate to get structured output and tools?