You need to visit /admin/plugins/discourse-ai/ai-personas and either create a new persona or enable one without tools. If you want to try an existing persona, Creative would be a good one to test as it doesn’t include any tools.
So you’d click edit here:
and at the bottom of the persona settings, you’ll need to enable it, click “create user”, and save your changes
Once that’s done, the Creative persona should appear in the list (you may need to refresh the page first)