add info on message limits

Author: ethanpalm

guides/assistant.mdx

@@ -18,6 +18,8 @@ The assistant uses agentic RAG (retrieval-augmented generation) with tool callin
 * **Cites sources** and provides navigable links to take users directly to referenced pages.
 * **Generates copyable code examples** to help users implement solutions from your documentation.
 
+Each message sent to the assistant counts toward your plan's message allowance. If you exceed your allowance, additional messages incur overage charges. You can set spending limits or disable the assistant if you reach your message allowance.
+
 You can view assistant usage through your dashboard to understand user behavior and documentation effectiveness. Export and analyze query data to help identify:
 
 * Frequently asked questions that might need better coverage.