Using API Extension with Tags/Multiselect Blueprint Field?

Is it possible to use an API Extension with a tags or multiselect field? I tried the following, but got authentication errors.

Seems like Kirby was treating the API as an external fetch and thus didn’t apply any existing authentication credentials; that makes sense for external API calls, but I’d love to use them for internal Panel use (and have them still be authenticated).

                label: Related Pages
                type: multiselect
                options: api
                  url: '{{ site.url }}/api/my-endpoint'

If you use something else but api (e.g. my-api), it should work.

Right, but I wanted to inherit the authentication requirements.