feat: additional instructions for the context file (#32)

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

Author: averikitsch

SPANNER.md

@@ -4,6 +4,11 @@ software delivery cycle.
 
 --
 
+# Setup
+
+## Required Gemini CLI Version
+
+To install this extension, the Gemini CLI version must be v0.6.0 or above. The version can be found by running: `gemini --version`.
 
 ## Spanner MCP Server (Data Plane: Connecting and Querying)
 
@@ -14,11 +19,37 @@ This section covers connecting to a Spanner instance.
     *   `SPANNER_PROJECT`: The GCP project ID.
     *   `SPANNER_INSTANCE`: The Spanner instance ID.
     *   `SPANNER_DATABASE`: The Spanner database ID.
-    * `SPANNER_DIALECT`: The Spanner database dialect e.g. "googlesql" or "postgresql"
+    *   `SPANNER_DIALECT`: The Spanner database dialect e.g. "googlesql" or "postgresql"
 
 2.  **Handle Missing Variables**: If a command fails with an error message containing a placeholder like `${SPANNER_PROJECT}`, it signifies a missing environment variable. Inform the user which variable is missing and instruct them to set it.
 
 3.  **Handle Permission Errors**: If you encounter permission errors, ensure the user has the correct Spanner permissions (e.g., `spanner.databases.get`, `spanner.databases.select`). The user likely lacks the role **Cloud Spanner Database User**
 (`roles/spanner.databaseUser`) or **Cloud Spanner Database Reader** (`roles/spanner.databaseReader`). You can provide these links for assistance:
     *   Granting Roles: https://cloud.google.com/iam/docs/grant-role-console
     *   Spanner Permissions: https://cloud.google.com/iam/docs/roles-permissions/spanner
+
+---
+
+# Usage Guidelines
+
+## Connecting to New Resources
+
+You will need to perform the following steps to change the current database connection:
+
+1.  **(Optional) Save your conversation:** To avoid losing your progress, save the current session by running the command: `/chat save <your-tag>`
+2.  **Stop the CLI:** Terminate the Gemini CLI.
+3.  **Update Environment Variables:** Set or update your environment variables (e.g. `SPANNER_INSTANCE`, `SPANNER_DATABASE`) to point to the new resource.
+4.  **Restart:** Relaunch the Gemini CLI
+5.  **(Optional) Resume conversation:** Resume your conversation with the command: `/chat resume <your-tag>`
+
+## Reusing Project Values
+
+Users may have set project environment variables:
+
+*   `SPANNER_PROJECT`: The GCP project ID.
+*   `SPANNER_INSTANCE`: The Spanner instance ID.
+*   `SPANNER_DATABASE`: The Spanner database ID.
+*   `SPANNER_DIALECT`: The Spanner database dialect e.g. "googlesql" or "postgresql"
+
+Instead of prompting the user for these values for specific tool calls, prompt the user to verify reuse a specific value.
+Make sure to not use the environment variable name like `SPANNER_PROJECT`, `${SPANNER_PROJECT}`, or `$SPANNER_PROJECT`. The value can be found by using command: `echo $SPANNER_PROJECT`.