Firebase functions onRequest to onCall

How do I pass this onRequest function to onCall? I am working from my localhost with emulators. Could someone give me some guidance, I have tried to follow the documentation of functions.https.onCall but I can't understand if I have to do any previous step.

export const getFileInformation = functions.https.onRequest( (req, res) => {

  return cors( req, res, () => {

    const urls = [
      `url1`,
      `url2`,
      `url3`
    ];

    const urlsCalls: any[] = [];
    const resultados: any[] = [];

    urls.forEach( url => {
      urlsCalls.push(axios.get(url));
    });

    Promise.allSettled(urlsCalls)
    .then( response => {
      response.map( (element: any) => {
        const item = element.value.data;
        resultados.push(item);
      });
      console.log(resultados);
      res.json(resultados);
    })
    .catch( error => {
      console.log(error);
    });
  } );
});

I'm trying something as simple as this:

export const getFileInformation2 = functions.https.onCall( (data, context) => {
  return { msg: 'Hello from Firebase!' };
});

But I get the following error:

{"error":{"message":"Bad Request","status":"INVALID_ARGUMENT"}}

How should I address an onCall function?