Update demo-deploy-on-g5k.md

demo-deploy-on-g5k.md

@@ -121,6 +121,10 @@ oarsub -S $HOME/myjob.sh
 ### API
 *[source](https://www.grid5000.fr/w/API)*
 
+When accessing the API from outside Grid'5000, you **MUST** send your Grid'5000 credentials (login and password) via the use of the HTTP Basic Authentication mechanism
+
+#### From inside
+
 - list in a JSON format clusters installed on Nantes site
   ```bash
   curl -sSfL -XGET https://api.grid5000.fr/3.0/sites/nantes/clusters | jq
@@ -136,8 +140,16 @@ oarsub -S $HOME/myjob.sh
   curl -sSfL -XGET https://api.grid5000.fr/3.0/sites/nantes/clusters/econome/nodes/econome-14 | jq
   ```
 
-- tunnel your ssh to grant access with your credentials to API commands
+#### From outside
+- tunnel your ssh to grant access using your credentials to perform API `POST` commands
   ```bash
   ssh -NL 3443:api.grid5000.fr:443 rirandriatoamanana@access.grid5000.fr
   ```
-  Go to https://localhost:3443
+  Go to https://localhost:3443 to check if ok by accessing to your account dashboard
+
+- - list a specific cluster, *e.g. econome*
+  ```bash
+  curl -k -XGET https://localhost:3443/sid/sites/nantes/clusters/econome | jq
+  ```
+
+