diff --git a/xx.md b/18.md
similarity index 73%
rename from xx.md
rename to 18.md
index e3ee60e..ab476d1 100644
--- a/xx.md
+++ b/18.md
@@ -55,19 +55,30 @@ Transport specifies methods for sending the ecash to the receiver. A transport c
 - a: target of Transport
 - g: optional tags for the Transport 
 
-There are different transport layers:
+### Transport types
 
-- nostr
-  - type: `nostr`
-  - target: `<nprofile>`
-  - tags: `[["1", "NIP-04"], ["2", "NIP-17"], ["3", "NIP-61"]]`
-- post
-  - type: `post`
-  - target: `<endpoint url>`
+The supported transport types are:
+
+#### Nostr
+
+- type: `nostr`
+- target: `<nprofile>`
+- tags: `[["NIP-04", "true"], ["NIP-17", "true"]]`
+
+The payment request MUST specify which type of Nostr message they support in the `tags`. For [NIP-04](https://github.com/nostr-protocol/nips/blob/master/04.md) and [NIP-17](https://github.com/nostr-protocol/nips/blob/master/17.md) direct messages, the sender sends a `PaymentRequestPayload` as the message content. 
+
+Note that the use of NIP-04 direct messages is strongly discouraged, since it reveals metadata about sender and receiver public keys.
+
+#### HTTP POST
+
+- type: `post`
+- target: `<endpoint url>`
+
+The execute the payment, the sender makes a `POST` request to the specified endpoint URL with the `PaymentRequestPayload` as the body.
 
 ## Payment payload
 
-Regardless of the transport layer, the payload sent to the receiver is a JSON serialized object as follows:
+If not specified otherwise, the payload sent to the receiver is a `PaymentRequestPayload` JSON serialized object as follows:
 
 ```json
 {
diff --git a/README.md b/README.md
index e0ca519..8bbb4fe 100644
--- a/README.md
+++ b/README.md
@@ -20,19 +20,20 @@ Wallets and mints `MUST` implement all mandatory specs and `CAN` implement optio
 
 ### Optional
 
-| #        | Description                       | Wallets                                                                     | Mints                                                   |
-| -------- | --------------------------------- | --------------------------------------------------------------------------- | ------------------------------------------------------- |
-| [07][07] | Token state check                 | [Nutshell][py], [Moksha][moksha], [Nutstash][ns], [cashu-ts][ts], [cdk-cli] | [Nutshell][py], [Moksha][moksha], [cdk-mintd], [nutmix] |
-| [08][08] | Overpaid Lightning fees           | [Nutshell][py], [Moksha][moksha], [Nutstash][ns], [cashu-ts][ts], [cdk-cli] | [Nutshell][py], [Moksha][moksha], [cdk-mintd], [nutmix] |
-| [09][09] | Signature restore                 | [Nutshell][py], [cdk-cli], [cashu-ts][ts], [gonuts]                         | [Nutshell][py], [cdk-mintd], [nutmix]                   |
-| [10][10] | Spending conditions               | [Nutshell][py], [cdk-cli], [cashu-ts][ts]                                   | [Nutshell][py], [cdk-mintd], [nutmix]                   |
-| [11][11] | Pay-To-Pubkey (P2PK)              | [Nutshell][py], [cdk-cli], [cashu-ts][ts]                                   | [Nutshell][py], [cdk-mintd], [nutmix]                   |
-| [12][12] | DLEQ proofs                       | [Nutshell][py], [cdk-cli]                                                   | [Nutshell][py], [cdk-mintd], [nutmix]                   |
-| [13][13] | Deterministic secrets             | [Nutshell][py], [Moksha][moksha], [cashu-ts][ts], [cdk-cli], [gonuts]       | -                                                       |
-| [14][14] | Hashed Timelock Contracts (HTLCs) | [Nutshell][py], [cdk-cli]                                                   | [Nutshell][py], [cdk-mintd], [nutmix]                   |
-| [15][15] | Partial multi-path payments (MPP) | [Nutshell][py]                                                              | [Nutshell][py], [nutmix]                                |
-| [16][16] | Animated QR codes                 | [Cashu.me][cashume]                                                         | -                                                       |
-| [17][17] | WebSocket subscriptions           | [Nutshell][py]                                                              | [Nutshell][py]                                          |
+| #        | Description                       | Wallets                                                                     | Mints                                         |
+| -------- | --------------------------------- | --------------------------------------------------------------------------- | --------------------------------------------- |
+| [07][07] | Token state check                 | [Nutshell][py], [Moksha][moksha], [Nutstash][ns], [cashu-ts][ts], [cdk-cli] | [Nutshell][py], [Moksha][moksha], [cdk-mintd] |
+| [08][08] | Overpaid Lightning fees           | [Nutshell][py], [Moksha][moksha], [Nutstash][ns], [cashu-ts][ts], [cdk-cli] | [Nutshell][py], [Moksha][moksha], [cdk-mintd] |
+| [09][09] | Signature restore                 | [Nutshell][py], [cdk-cli], [cashu-ts][ts], [gonuts]                         | [Nutshell][py], [cdk-mintd]                   |
+| [10][10] | Spending conditions               | [Nutshell][py], [cdk-cli], [cashu-ts][ts]                                   | [Nutshell][py], [cdk-mintd], [nutmix]         |
+| [11][11] | Pay-To-Pubkey (P2PK)              | [Nutshell][py], [cdk-cli], [cashu-ts][ts]                                   | [Nutshell][py], [cdk-mintd], [nutmix]         |
+| [12][12] | DLEQ proofs                       | [Nutshell][py], [cdk-cli]                                                   | [Nutshell][py], [cdk-mintd]                   |
+| [13][13] | Deterministic secrets             | [Nutshell][py], [Moksha][moksha], [cashu-ts][ts], [cdk-cli], [gonuts]       | -                                             |
+| [14][14] | Hashed Timelock Contracts (HTLCs) | [Nutshell][py], [cdk-cli]                                                   | [Nutshell][py], [cdk-mintd]                   |
+| [15][15] | Partial multi-path payments (MPP) | [Nutshell][py]                                                              | [Nutshell][py]                                |
+| [16][16] | Animated QR codes                 | [Cashu.me][cashume]                                                         | -                                             |
+| [17][17] | WebSocket subscriptions           | [Nutshell][py]                                                              | [Nutshell][py]                                |
+| [18][18] | Payment requests                 | [Cashu.me][cashume], [Boardwalk][bwc]                                                        | -   
 
 #### Wallets:
 
@@ -45,7 +46,7 @@ Wallets and mints `MUST` implement all mandatory specs and `CAN` implement optio
 - [Nutstash][ns]
 - [Cashu.me][cashume]
 - [Gonuts][gonuts]
-- [Boardwalk Cash][bwc]
+- [Boardwalk][bwc]
 
 #### Mints:
 
@@ -87,3 +88,4 @@ Wallets and mints `MUST` implement all mandatory specs and `CAN` implement optio
 [15]: 15.md
 [16]: 16.md
 [17]: 17.md
+[18]: 18.md