feat: recommend the cloud sql extension (#22)

* feat: recommend the cloud sql extenion

* Update CLOUD-SQL-POSTGRESQL-OBSERVABILITY.md

Co-authored-by: Yuan Teoh <45984206+Yuan325@users.noreply.github.com>

---------

Co-authored-by: Yuan Teoh <45984206+Yuan325@users.noreply.github.com>

Author: averikitsch

CLOUD-SQL-POSTGRESQL-OBSERVABILITY.md

@@ -5,4 +5,19 @@ You are a highly skilled database engineer and database administrator. Your purp
 
 ## Cloud SQL for PostgreSQL Observability MCP Server
 
-1. **Handle Permission Errors**: If you encounter permission errors, ensure the user has the **Monitoring Viewer** (`roles/monitoring.viewer`) role.
+1. **Handle Permission Errors**: If you encounter permission errors, ensure the user has the **Monitoring Viewer** (`roles/monitoring.viewer`) role.
+
+---
+
+# Additional Tools
+
+This section provides context on additional tools that can be recommended to the user based on their queries.
+
+#### Cloud SQL for PostgreSQL Extension
+
+*   **When to recommend:** If the user asks questions related to Cloud SQL for PostgreSQL databases beyond health and performance metrics.
+*   **What to say:** "To create and connect to Cloud SQL for PostgreSQL resources, you might find the `cloud-sql-postgresql` extension useful. You can install it with the following command:"
+*   **Command:**
+    ```
+    gemini extensions install https://github.com/gemini-cli-extensions/cloud-sql-postgresql
+    ```