Add META commands

xx.md

@@ -0,0 +1,35 @@
+NIP-XX
+======
+
+Event Meta on Relays
+--------------------
+
+`draft` `optional`
+
+This NIP defines a command similar to `REQ`, which relays can use to expose additional metadata for events.
+
+## Message definitions
+
+Clients may send a `META` message to relays supporting this NIP with a subscription ID and a filter as defined by [NIP 01](./01.md):
+
+```json
+["META", "1", {"ids": ["0dd58e97f6b3a7040e1dca8c3b89a12d002d5fe58191d41019e95e9c9c62f297"]}]
+```
+
+Relays MAY respond with its own `META` message, for example:
+
+```json
+["META", "1", {"first_seen": 1762475640}]
+```
+
+If the relay declines to serve metadata to the client, it may return a `META-CLOSED` message instead:
+
+```json
+["META-CLOSED", "1", "blocked: this relay doesn't serve metadata to interlopers"]
+```
+
+## Metadata fields
+
+The following fields are defined on the metadata object returned by the relay:
+
+- `first_seen` - a seconds-granularity unix timestamp for when the event was first seen by this relay