diff --git a/README.md b/README.md
index 941369d..4d851aa 100644
--- a/README.md
+++ b/README.md
@@ -2,10 +2,14 @@
 
 Authentication (AuthN) and Authorization (AuthZ) data management.
 
-## Installation
+## Requirements
 
 You need [Docker](https://docs.docker.com/engine/) and [Docker-compose](https://docs.docker.com/compose/).
 
+A RabbitMQ instance is also required to send / receive messages when data has been inserted/updated/deleted.
+
+## Installation
+
 Copy `.env.dist` to `.env` :
 
 ```bash
@@ -38,25 +42,62 @@ docker exec v3_user sh -c "npx prisma migrate dev"
 
 ## Usage
 
-The app exposes the following [gRPC](https://grpc.io/) services :
+The app is used for authentication (aka AuthN) and authorization (aka AuthZ : _to be developped_).
 
--   **Create** : create an auth
+AuthN consists in verifying a username / password couple. A user can have multiple usernames (representing multiple identifiers), all of them sharing the same password. In the app, all the authentication information about a user is called an _auth_. As of 2022/10/23, the possible identifiers are :
+
+-   an email
+-   a phone number
+
+Note that all usernames are unique in the system : many users can't have the same email or phone number.
+
+For AuthN, the app exposes the following [gRPC](https://grpc.io/) services :
+
+-   **Create** : create an auth with one username / password (you can't create multiple usernames at once)
 
     ```json
     {
         "uuid": "30f49838-3f24-42bb-a489-8ffb480173ae",
         "username": "john.doe@email.com",
-        "password": "John123"
+        "password": "John123",
+        "type": "EMAIL"
     }
     ```
 
--   **Update** : update an auth (username and/or password)
+-   **AddUsername** : add a username to an auth
+
+    ```json
+    {
+        "uuid": "30f49838-3f24-42bb-a489-8ffb480173ae",
+        "username": "+33611223344",
+        "type": "PHONE"
+    }
+    ```
+
+-   **UpdateUsername** : update a username
 
     ```json
     {
         "uuid": "30f49838-3f24-42bb-a489-8ffb480173ae",
         "username": "johnny.doe@email.com",
-        "password": "John1234"
+        "type": "EMAIL"
+    }
+    ```
+
+-   **DeleteUsername** : delete a username (an error is thrown if it's the only username of an auth, as an auth **must** have at least one associated username)
+
+    ```json
+    {
+        "username": "+33611223344"
+    }
+    ```
+
+-   **UpdatePassword** : update the password of an auth
+
+    ```json
+    {
+        "uuid": "30f49838-3f24-42bb-a489-8ffb480173ae",
+        "password": "Johnny123"
     }
     ```
 
@@ -65,10 +106,22 @@ The app exposes the following [gRPC](https://grpc.io/) services :
     ```json
     {
         "username": "john.doe@email.com",
-        "password": "John123"
+        "password": "Johnny123"
     }
     ```
 
+-   **Delete** : delete an auth and its associated usernames
+
+    ```json
+    {
+        "uuid": "30f49838-3f24-42bb-a489-8ffb480173ae"
+    }
+    ```
+
+## Messages
+
+Various RabbitMQ messages are sent for logging purpose.
+
 ## Test
 
 ```bash