As I understand it, there's no real way to enforce access rights inside an LLM. If the bot has access to some data, and you have access to the bot, you can potentially trick it into coughing up the data regardless of whether you're supposed to see that info or not.
MCP tools with OAuth support + RFC 8693 OAuth 2.0 Token Exchange (aka OAuth 2.0 On-Behalf-Of flow in Azure Entra - though I don't think MCP 2025-06-18 accounts for the RFC 8693) could be used to limit the MCP bot responses to what the current user is authorized to see.