Participants should always be informed of being recorded. The best practices are to either inform them before the meeting, or at the beginning of the meeting.

You can attach in the calendar invite: "This session will be recorded for training and quality purposes. We can also send you a link to the recording, so you can review it. If you don't wish to be recorded, no problem. Simply let us know and we'll stop the recording at any time."

Or when the meeting starts: "Is it okay if I record this meeting to improve the quality, and also so I can focus on listening to you instead of dividing my attention into taking notes? I can also share the recording with you afterwards if you'd like."

In our experience being in thousands of calls, the participants appreciate the recording for many reasons: you can be present in the conversation, there's a recording to revisit, and it can be shared later to people who couldn't attend!