diff --git a/57.md b/57.md
index f6fa4cc..bbeb629 100644
--- a/57.md
+++ b/57.md
@@ -30,7 +30,7 @@ Having lightning receipts on nostr allows clients to display lightning payments
 
 3. Clients may choose to display a lightning zap button on each post or on the users profile, if the user's lnurl pay request endpoint supports nostr, the client SHOULD generate a `zap invoice` instead of a normal lnurl invoice.
 
-4. To generate a `zap invoice`, call the `callback` url with `amount` set to the milli-satoshi amount value. A `nostr` querystring value MUST be set as well. It is a uri-encoded `zap request` note signed by the user's key. The `zap request` note contains an `e` tag of the note it is zapping, and a `p` tag of the target user's pubkey. The `e` tag is optional which allows profile tipping. The `zap request` note must also have a `relays` tag, which is gathered from the user's configured relays. The `zap request` note SHOULD contain an `amount` tag, which is the milli-satoshi value of the zap which clients SHOULD verify being equal to the amount of the invoice. The `content` MAY be an additional comment from the user which can be displayed when listing zaps on posts and profiles.
+4. To generate a `zap invoice`, call the `callback` url with `amount` set to the milli-satoshi amount value. A `nostr` querystring value MUST be set as well. It is a uri-encoded `zap request` note signed by the user's key. The `zap request` note contains an `e` tag of the note it is zapping, and a `p` tag of the target user's pubkey. The `e` tag is optional which allows profile tipping. An optional `a` tag allows tipping parameterized replaceable events such as NIP-23 long-form notes. The `zap request` note must also have a `relays` tag, which is gathered from the user's configured relays. The `zap request` note SHOULD contain an `amount` tag, which is the milli-satoshi value of the zap which clients SHOULD verify being equal to the amount of the invoice. The `content` MAY be an additional comment from the user which can be displayed when listing zaps on posts and profiles.
 
 5. Pay this invoice or pass it to an app that can pay the invoice. Once it's paid, a `zap note` will be created by the `zapper`.
 
@@ -58,6 +58,8 @@ The lnurl server will need some additional pieces of information so that clients
 
 	f. If there is an `amount` tag, it MUST be equal to the `amount` query parameter.
 
+	g. If there is an `a` tag, it MUST be a valid NIP-33 event coordinate
+
 5. If valid, fetch a description hash invoice where the description is this note and this note only. No additional lnurl metadata is included in the description.
 
 At this point, the lightning node is ready to send the zap note once payment is received.