docs: update README with node prerequisites, codex installation and troubleshooting

Author: belluru

README.md

@@ -22,7 +22,7 @@ Ensure you have the following installed:
 * **Node.js and npm** (Latest version recommended)
 * One of the following coding agents:
     * [Gemini CLI](https://github.com/google-gemini/gemini-cli) (v0.6.0+)
-    * [Claude Code](https://docs.anthropic.com/en/docs/agents-and-tools/claude-code/overview)
+    * [Claude Code](https://code.claude.com/docs)
     * Codex CLI
 * **(Optional) IDE Extension:** [Google Cloud Data Agent Kit](https://docs.cloud.google.com/data-cloud-extension/vs-code/install).
 
@@ -81,6 +81,10 @@ MCP toolboxes are added to the respective agent configuration files. You must co
 
 In all cases, you must restart the agent after updating the configuration files.
 
+To verify your configuration:
+* Run the `/mcp` command to check the status of available MCP servers.
+* Ask your agent "What skills are available?" to view the list of active skills.
+
 <details>
 <summary><b>Gemini CLI and Gemini Code Assist</b></summary>