Nip88: Adding dtag, typos

- A kind 37001 dtag is referenced in the 7003 description, but was missing in the example

-A etag is referenced in the  kind 7001 description but an a tag was referenced in the example

88.md

@@ -0,0 +1,171 @@
+NIP-88
+======
+
+Recurring Subscriptions
+-----------------------
+
+`draft` `optional`
+
+This NIP defines a way for a pubkey to create recurring subscription payments to another pubkey.
+
+Actors in this flow:
+* Recipient: A pubkey that receives recurring payments
+* Subscriber: A pubkey that sends recurring payments
+* Payment verifier: An optional pubkey recipients can designate to verify payments on their behalf
+
+# Kinds
+`kind:37001` - Tier Event -- Optionally published by recipients
+`kind:7001` - Subscribe Event -- Published by subscribers
+`kind:7002` - Unsubscribe Event -- Published by subscribers
+`kind:7003` - Subscription Payment Receipt -- Published by payment-verifier-pubkey
+
+## `kind:37001`: Tier Event
+A pubkey that wants to provide others the ability to subscribe to them can create "tiers". These tiers might provide certain benefits to the supporters who subscribe to these.
+
+```js
+{
+    "kind": 37001,
+    "content": "<description of the tier>",
+    "tags": [
+        [ "title", "..." ],
+        [ "image", "..." ],
+
+        // Perks
+        [ "perk", "<description>" ],
+        [ "perk", "<description>" ],
+
+        // Amount possibilities
+        [ "amount", "<amount-in-base-unit>", "currency", "<monthly>" ],
+        [ "amount", "<amount-in-base-unit>", "currency", "<quarterly>" ],
+
+        // Zap-splits
+        [ "zap", "<recipient-pubkey>", "relay-url", "19" ], // 95%
+        [ "zap", "", "relay-url", "1" ], // 5%
+
+        // Relay and payment-verification
+        [ "r", "wss://my-subscribers-only-relay.com" ],
+        [ "p", "<payment-verifier-pubkey>" ],
+
+        // A unique identifier
+        [ "d", "<random-id>" ],
+    ]
+}
+```
+
+`.content`: description of what subscribers can expect.
+Tag `title` is an optional title for the tier.
+Tag `image` is an optional image for the tier.
+Zero or more `perk` tags specify the benefits of the tier; these can be rendered as a list of benefits to the user in addition to the content.
+One or more `amount` tags specify the payment required for this tier and its cadence.
+    * The first argument should be the stringified amount in cents or msats, and the second argument the currency
+    * The third argument SHOULD be one of `daily`, `monthly`, `yearly`
+One or more `amount` tags MUST exist.
+Zero or more `zap` tags can exist as defined in NIP-57.
+
+A `zap` tag with no pubkey indicates that the client can include any pubkey in the `kind:7001` event (and in the resulting recurring zaps). This way, users can offer a "referral" fee to other clients.
+
+An `r` tag can be included to specify a relay where clients can find special content for this tier.
+
+Zero or more `p` tags can be included to specify a pubkey that is trusted by the tier creator to verify payments on their behalf.
+
+#### Examples
+* `[ "amount", "100", "usd", "daily" ]`, $1.00 a day.
+* `[ "amount", "1000000", "msats", "daily" ]`, 1000000 millisats a day.
+
+## Subscribe Event
+
+```js
+{
+    "kind": 7001,
+    "content": "<optional-message>",
+    "tags": [
+        [ "p", "<recipient-pubkey>" ],
+        [ "e", "<supporting-tier-event-id>" ],
+        [ "event", "<stringied-event-subscribed-to>" ],
+        [ "amount", "<amount-in-base-unit>", "<currency>", "<cadence>" ],
+
+        // Zap-splits
+        [ "zap", "<recipient-pubkey>", "19" ], // 95%
+        [ "zap", "fa984bd7dbb282f07e16e7ae87b26a2a7b9b90b7246a44771f0cf5ae58018f52", "1" ], // 5% to client developer where subscription was created
+    ]
+}
+```
+
+When a user wants to subscribe to support a user they create a `kind:7001` event.
+
+* `.content` is an optional message the supporter can write.
+* The `p` tag MUST tag the pubkey being supported.
+* The `e` tag is optional; it should point to a `kind:37001` support tier event. There MUST be exactly 0 or 1 `e` tag.
+* The `event` tag is optional; subscribers can opt to keep the version of the event they subscribed to. There MUST be exactly 0 or 1 `event` tag.
+* The `amount` tag specifies what the supporters is committing to pay to the supported pubkey and the cadence. MUST be equal to one of the amounts specified in the
+`kind:37001` event if one is tagged. There MUST be exactly 1 `amount` tag.
+
+The `kind:7001` event can be created without an `e` tag so that users can create recurring support events without the pubkey receiving the support having explicitly created a support tier.
+
+### Zap splits
+`kind:7001` events can include zap splits as defined in NIP-57. Zap splits MUST be copied by clients as they exist in the `kind:37001` event being subscribed to. When an event has a `zap` tag with no pubkey, clients can discard it, or add the client developer's pubkey, or any other user they wish to receive a share of recurring subscriptions.
+
+## Paying
+The supporting user should create a zap `p`-tagging the receiver and e-tagging the `kind:7001`. There MUST be a single `p` and a single `e` tag in the zap request.
+
+```js
+{
+    "kind": 9734,
+    "content": "",
+    "tags": [
+        [ "p", "<recipient-pubkey>" ],
+        [ "e", "<kind-7001-event-id>" ]
+    ]
+}
+```
+
+Clients supporting this NIP can check for zaps e-tagging the `kind:7001` event to find the pubkeys that have a valid, paid subscriptions at each different period.
+
+The same `kind:7001` is re-zapped on a regular basis per the cadence specified in the event.
+
+## Stopping a subscription
+A user who wants to signal they are no longer subscribed can publish a `kind:7002` event tagging the `kind:7001` they are stopping and `p`-tagging the pubkey they are no longer subscribed to.
+
+```js
+{
+    "kind": 7002,
+    "content": "<optional-message>",
+    "tags": [
+        [ "p", "<recipient-pubkey>" ],
+        [ "e", "<kind-7001-event-id>" ],
+    ]
+}
+```
+
+## Subscription Payment Receipt
+When a subscription payment is made and a `payment-verifier-pubkey` is set on the `kind:37001` this pubkey publishes `kind:7003` events tagging the `kind:7001` event that was paid and `p`-tagging the pubkey that received the payment.
+
+```js
+{
+    "kind": 7003,
+    "content": "<optional-message>",
+    "tags": [
+        [ "p", "<recipient-pubkey>" ],
+        [ "P", "<subscriber-pubkey>" ],
+        [ "e", "<kind-7001-event-id>" ],
+        [ "valid", "<from-timestamp>", "<to-timestamp>" ]
+        [ "tier", "kind:37001-d-tag" ]
+    ]
+}
+```
+
+`p` is the pubkey that received the payment.
+`P` is the pubkey that made the payment.
+`e` is the `kind:7001` event that was paid.
+`valid` is the period for which the payment is valid.
+`tier` is the d-tag of the `kind:37001` that this subscription is for.
+
+# Appendix 0: Verifying Payment
+The following conditions must be met to verify a payment:
+
+* Time between zap receipts should be equal or less than the cadence specified in the `kind:7001` event.
+* Amount of the zap receipt should be equal or greater than the amount specified in the `kind:7001` event. For currencies not directly supported by the zap spec, clients should do a best effort conversion to the currency specified in the `kind:7001` event at the time of zap receipt.
+* Zap-receipts should include a zap request `e`-tagging the `kind:7001` event. Zap-receipts might not include a signature (for NWC-automated payments where the subscriber is not present to sign the zap request).
+* Validations specified in [NIP-57](https://github.com/nostr-protocol/nips/blob/master/57.md).
+
+If `kind:7003` events are published by the payment-verifier-pubkey, clients can use these to verify payments more simply.

README.md

@@ -103,6 +103,8 @@ They exist to document what may be implemented by [Nostr](https://github.com/nos
 | `5000`-`5999` | Job Request                | [90](90.md)                        |
 | `6000`-`6999` | Job Result                 | [90](90.md)                        |
 | `7000`        | Job Feedback               | [90](90.md)                        |
+| `7001`        | Subscription Start         | [88](88.md)                        |
+| `7002`        | Subscription Stop          | [88](88.md)                        |
 | `9041`        | Zap Goal                   | [75](75.md)                        |
 | `9734`        | Zap Request                | [57](57.md)                        |
 | `9735`        | Zap                        | [57](57.md)                        |
@@ -148,6 +150,7 @@ They exist to document what may be implemented by [Nostr](https://github.com/nos
 | `31989`       | Handler recommendation     | [89](89.md)                        |
 | `31990`       | Handler information        | [89](89.md)                        |
 | `34550`       | Community Definition       | [72](72.md)                        |
+| `37001`      | Subscription Tier           | [88](88.md)                        |
 
 [nostrocket-1971]: https://github.com/nostrocket/NIPS/blob/main/Problems.md