You are not returning any value from the “mycaller” function. Also, since you’re already in an “async” function you can just await the call and get the response, without using “then”.
For example:
Change the handler function:
...
output = await mycaller(event.prompt);
...
And change mycaller
async function mycaller(prompt) {
const response = await getResponse(prompt);
return res.data.choices[0].text;
}