How do hide Azure function app from search results ?

What is the correct way to hide the published Azure function app from search result ?

For an eventual consistent systems the Azure Function app is mostly the backend that a client or a server can access. So it needs to be hidden from searches.

I tried adding a RobotsEndpoint function but the function URL will have a api/{robots.txt} route name and thus it is no longer in the root directory.

How to explicitly add robots.txt
User-agent: *
Disallow: /

Start by reviewing Azure Functions routing behavior for a RobotsEndpoint function and the generated api/{robots.txt} route. Check whether the platform supports a root-level robots.txt containing User-agent: * and Disallow: /. Done means the published app serves that content from the root URL rather than under /api.

Written by the indexing model from the issue text.