2 files changed, 148 insertions, 3 deletions

diff --git a/87.md b/87.md
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+++ b/87.md
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+NIP-87
+======
+
+Ecash Mint Discoverability
+--------------------------------
+
+`draft` `optional`
+
+This NIP describes `kind:38173`, `kind:38172` and `kind:38000`: a way to discover ecash mints, their capabilities, and people who recommend them.
+
+## Rationale
+
+Nostr's discoverability and transparent event interaction is one of its most interesting/novel mechanics.
+This NIP provides a simple way for users to discover ecash mints recommended by other users and to interact with them.
+
+### Parties involved
+
+There are three actors to this workflow:
+
+* An ecash mint operator, announces their mint and its capabilities.
+    * Publishes `kind:38173` or `kind:38172`, detailing how to connect to it and its capabilities.
+* user A, who recommends an ecash mint
+    * Publishes `kind:38000`
+* user B, who seeks a recommendation for an ecash mint
+    * Queries for `kind:38000` and, based on results, queries for `kind:38173`/`kind:38172`
+
+## Events
+
+### Recommendation event
+```json
+{
+  "kind": 38000,
+  "pubkey": <recommender-user-pubkey>,
+  "tags": [
+    ["k", "38173"],
+    ["d", "<d-identifier>"],
+    ["u", <recommended-fedimint-invite-code>],
+    ["a", "38173:fedimint-pubkey:<d-identifier>", "wss://relay1"]
+  ],
+  "content": "I trust this mint with my life"
+}
+```
+
+The recommendation event is a parameterized-replacable event so that a user can change edit their recommendation without creating a new event.
+
+The `d` tag in `kind:38000` is the `kind:38173`/`kind:38172` event identifier this event is recommending, if no event exists, the `d` tag can still be calculated from the mint's pubkey/id.
+The `k` tag is the kind number that corresponds to the event kind that the user is recommending, in this case `kind:38173` for fedimints and `kind:38172` for cashu mints.
+
+Optional `u` tags can be added to give a recommend way to connect to the mint.
+The value of the tag is the URL or invite code of the ecash mint.
+Multiple `u` tags can appear on the same `kind:38000`.
+
+`a` tags are used to point to the `kind:38173`/`kind:38172` event of the ecash mint.
+The first value of the tag is the `kind:38173`/`kind:38172` event identifier, the second value of the tag is a relay hint.
+This is used to correctly point to the mint's `kind:38173`/`kind:38172` event in case there are duplicates claiming to be the same mint.
+
+The content can be used to give a review.
+
+## Ecash Mint Information
+
+Cashu mints SHOULD publish `kind:38172` events to announce their capabilities and how to connect to them.
+
+For cashu mints, the `u` tag SHOULD be the URL to the cashu mint and it should list the nuts that the cashu mint supports.
+
+The `d` tag SHOULD be the mint's pubkey (found when querying `/v1/info`), this way users can query by pubkey and find the mint announcement.
+
+An `n` tag SHOULD be added to signify the network the cashu mint is on (either `mainnet`, `testnet`, `signet`, or `regtest`)
+
+```json
+{
+  "kind": 38172,
+  "pubkey": "<application-pubkey>",
+  "content": "<optional-kind:0-style-metadata>",
+  "tags": [
+    ["d", <cashu mint pubkey>],
+    ["u", "https://cashu.example.com"],
+    ["nuts", "1,2,3,4,5,6,7"],
+    ["n", "mainnet"]
+  ]
+}
+```
+
+Fedimints SHOULD publish `kind:38173` events to announce their capabilities and how to connect to them.
+
+For fedimints, it should list all known fedimint invite codes in `u` tags and it should list the modules it supports.
+
+The `d` tag SHOULD be the federation id, this way users can query by federation id and find the fedimint announcement.
+
+An `n` tag SHOULD be added to signify the network the fedimint is on (either `mainnet`, `testnet`, `signet`, or `regtest`)
+
+```json
+{
+  "kind": 38173,
+  "pubkey": "<application-pubkey>",
+  "content": "<optional-kind:0-style-metadata>",
+  "tags": [
+    ["d", <federation-id>],
+    ["u", "fed11abc.."],
+    ["u", "fed11xyz.."],
+    ["modules", "lightning,wallet,mint"],
+    ["n", "signet"]
+  ]
+}
+```
+
+* `content` is an optional `metadata`-like stringified JSON object, as described in NIP-01. This content is useful when the pubkey creating the `kind:38173` is not a normal user. If `content` is empty, the `kind:0` of the pubkey should be used to display mint information (e.g. name, picture, web, LUD16, etc.)
+
+## Example
+
+### User A recommends some mints
+User A might be a user of a cashu mint. Using a client, user A publishes an event recommending the cashu mint they use.
+
+```json
+{
+  "kind": 38000,
+  "tags": [
+    ["u", "fed11abc..", "fedimint"],
+    ["u", "https://cashu.example.com", "cashu"],
+    ["a", "38173:fedimint-pubkey:<d-identifier>", "wss://relay1", "fedimint"],
+    ["a", "38172:cashu-mint-pubkey:<d-identifier>", "wss://relay2", "cashu"]
+  ],
+  ...
+}
+```
+
+### User B finds a mint
+User B wants to use an ecash wallet, they need to find a mint.
+
+User B's wallet client queries for `kind:38000` events, looking for recommendations for ecash mints.
+
+```json
+["REQ", <id>, [{ "kinds": [38000], "authors": [<user>, <users-contact-list>], "#k": ["38173"] }]]
+```
+
+User B, who follows User A, sees that `kind:38000` event and tries to connect to the corresponding mints.
+
+### Alternative query bypassing `kind:38000`
+Alternatively, users might choose to query directly for `kind:38173` for an event kind. Clients SHOULD be careful doing this and use spam-prevention mechanisms or querying high-quality restricted relays to avoid directing users to malicious handlers.
+
+```json
+["REQ", <id>, [{ "kinds": [38173], "authors": [...] }]]
+```
diff --git a/README.md b/README.md
index 397eceb..ff7e9bb 100644
--- a/README.md
+++ b/README.md
@@ -93,6 +93,7 @@ They exist to document what may be implemented by [Nostr](https://github.com/nos
 - [NIP-7D: Threads](7D.md)
 - [NIP-84: Highlights](84.md)
 - [NIP-86: Relay Management API](86.md)
+- [NIP-87: Ecash Mint Discoverability](87.md)
 - [NIP-88: Polls](88.md)
 - [NIP-89: Recommended Application Handlers](89.md)
 - [NIP-90: Data Vending Machines](90.md)
@@ -107,7 +108,6 @@ They exist to document what may be implemented by [Nostr](https://github.com/nos
 - [NIP-C7: Chats](C7.md)
 
 ## Event Kinds
-
 | kind          | description                     | NIP                                    |
 | ------------- | ------------------------------- | -------------------------------------- |
 | `0`           | User Metadata                   | [01](01.md)                            |
@@ -200,6 +200,7 @@ They exist to document what may be implemented by [Nostr](https://github.com/nos
 | `10166`       | Relay Monitor Announcement      | [66](66.md)                            |
 | `13194`       | Wallet Info                     | [47](47.md)                            |
 | `17375`       | Cashu Wallet Event              | [60](60.md)                            |
+| `17375`       | Ecash Mint Recommendation       | [87](87.md)                            |
 | `21000`       | Lightning Pub RPC               | [Lightning.Pub][lnpub]                 |
 | `22242`       | Client Authentication           | [42](42.md)                            |
 | `23194`       | Wallet Request                  | [47](47.md)                            |
@@ -247,9 +248,11 @@ They exist to document what may be implemented by [Nostr](https://github.com/nos
 | `31924`       | Calendar                        | [52](52.md)                            |
 | `31925`       | Calendar Event RSVP             | [52](52.md)                            |
 | `31989`       | Handler recommendation          | [89](89.md)                            |
-| `31990`       | Handler information             | [89](89.md)                            |                         |
-| `32267`       | Software Application            |                                        |                        |
+| `31990`       | Handler information             | [89](89.md)                            |
+| `32267`       | Software Application            |                                        |
 | `34550`       | Community Definition            | [72](72.md)                            |
+| `38172`       | Cashu Mint Announcement         | [87](87.md)                            |
+| `38173`       | Fedimint Announcement           | [87](87.md)                            |
 | `38383`       | Peer-to-peer Order events       | [69](69.md)                            |
 | `39000-9`     | Group metadata events           | [29](29.md)                            |
 | `39089`       | Starter packs                   | [51](51.md)                            |