diff --git a/README.md b/README.md
index 08fbb9a..f1bd7e7 100644
--- a/README.md
+++ b/README.md
@@ -39,14 +39,18 @@ pip install frequenz-client-reporting==$VERSION
 
 ```python
 from datetime import datetime, timedelta
+import os
 
 from frequenz.client.common.metric import Metric
 from frequenz.client.reporting import ReportingApiClient
 
 # Change server address
 SERVER_URL = "grpc://replace-this-with-your-server-url:port"
-API_KEY = open('api_key.txt').read().strip()
-client = ReportingApiClient(server_url=SERVER_URL, key=API_KEY)
+AUTH_KEY = os.environ['REPORTING_API_AUTH_KEY'].strip()
+# It is recommended to use a proper secret store to get the secret
+# For local development, make sure not to leave it in the shell history
+SIGN_SECRET= os.environ['REPORTING_API_SIGN_SECRET'].strip()
+client = ReportingApiClient(server_url=SERVER_URL, auth_key=AUTH_KEY, sign_secret=SIGN_SECRET)
 ```
 
 Besides the `microgrid_id`, `component_id`s, `metrics`, start, and end time,
@@ -157,7 +161,8 @@ microgrid component data from the reporting API.
 ```bash
 reporting-cli \
     --url localhost:4711 \
-    --key=$(<api_key.txt)
+    --auth_key=$AUTH_KEY
+    --sign_secret=$SIGN_SECRET
     --mid 42 \
     --cid 23 \
     --metrics AC_ACTIVE_POWER AC_REACTIVE_POWER \
diff --git a/RELEASE_NOTES.md b/RELEASE_NOTES.md
index 44299b0..0663a9f 100644
--- a/RELEASE_NOTES.md
+++ b/RELEASE_NOTES.md
@@ -6,13 +6,14 @@
 
 ## Upgrading
 
-<!-- Here goes notes on how to upgrade from previous versions, including deprecations and what they should be replaced with -->
+* The `key` parameter of the client has been renamed to `auth_key`
 
 ## New Features
 
 * Add HMAC generation capabilities.
-    * The new CLI option "key" can be used to provide the server's key.
-    * The client itself now has a "key" argument in the constructor.
+    * The new CLI option "sign_secret" can be used to provide the server's HMAC secret.
+    * The client itself now has a "sign_secret" argument in the constructor.
+    * Update documentation describing how to use the above options.
 
 ## Bug Fixes
 
diff --git a/src/frequenz/client/reporting/cli/__main__.py b/src/frequenz/client/reporting/cli/__main__.py
index 6f0563b..9085055 100644
--- a/src/frequenz/client/reporting/cli/__main__.py
+++ b/src/frequenz/client/reporting/cli/__main__.py
@@ -102,7 +102,7 @@ def main() -> None:
             states=args.states,
             bounds=args.bounds,
             service_address=args.url,
-            auth_key=args.key,
+            auth_key=args.auth_key,
             fmt=args.format,
             sign_secret=args.sign_secret,
         )