illegal offset type?

I just took my simple chatgpt call and am trying to move it to a function so i cloned my api call, removed everything else, then told it to make this one api call into a function. i added 'query' as only parameter

now when I run it I get 'illegal offset type' and no real way to troubleshoot it in debug log.

I'm wondering if its obvious what I'm doing wrong and I'm just not seeing it, but the api call is exactly the same as from the original API . Not quite sure how to troubleshoot with such limited information.

my input to this Run & Debug is {"query":"hello chat"}