This could be done automatically by pinging the root and searching for a header set by railway's default page. If it doesn't exist then the service is live.
We used to do that by default, but it led to issues with load on our proxy. (Imagine n * m pings against your host for a shit-tonne (official measurement) of builds + deploys a day.)
We are hiring Network Engineers for exactly this reason :')
We are hiring Network Engineers for exactly this reason :')