I've started tagging relays that are monitored by my NIP66 monitor to include the "T" tag. What does this mean? It means client devs could use this to find "Directory" or "PrivateInbox" relays by searching NIP66 events. This solves nostr discovery.
It also means that if you run a relay(s) that provide a service described by this list you should monitor and tag them! This will make them searchable via the PascalCase descriptions.
As per the NIP66 Specification https://github.com/nostr-protocol/nips/blob/master/66.md
The tool I use to publish monitors (possibly the only open source one) has these changes on master branch. Release soon.

GitHub
Relay Type Nomenclature · Issue #1282 · nostr-protocol/nips
We need to find good labels for each relay type. Apps need to request users to put a relay of a given type in certain fields, and relays need help ...
GitHub
GitHub - relaytools/monitorlizard: Monitoring of relays with output formats for distribution over nostr (nip66) and InfluxDB
Monitoring of relays with output formats for distribution over nostr (nip66) and InfluxDB - relaytools/monitorlizard