To set up SMS notifications for critical events in Cloud Monitoring, what is a necessary step?

To set up SMS notifications for critical events in Cloud Monitoring, the registration of team members' phone numbers is essential. This step ensures that the system has the necessary contact information to send SMS alerts directly to the individuals who need to be informed of critical events. Properly registering phone numbers allows Cloud Monitoring to effectively deliver notifications via SMS, which is crucial for real-time awareness and prompt responses to potential issues.

The other options don't align with the process of establishing SMS notifications. Although webhooks and third-party tools can be utilized for various notification types, they are not specifically required for SMS alerts. Enabling email alerts does not equate to setting up SMS notifications, as this action pertains to a different mode of communication altogether. Therefore, ensuring that team members have registered their phone numbers is a fundamental requirement for effective SMS notification implementation in Cloud Monitoring.