What indicates if an Apex script has failed during deployment?

The errors tab in the destination org is critical in indicating if an Apex script has failed during deployment because it provides detailed information about any errors that occurred during the execution of Apex code. When deploying changes to Salesforce, the deployment process compiles and executes the code, and if any issues arise, they are logged in this errors tab. This feature enables developers and administrators to quickly identify and troubleshoot issues, facilitating a smoother deployment process.

On the other hand, an execution log provides a record of what was executed during the deployment but may not explicitly indicate failures. Email notifications typically inform recipients about the overall status of the deployment but do not contain detailed error information and may not be generated for every type of failure. A warning sign in the deployment task might signal potential issues but does not provide comprehensive details about failures, making the errors tab the most direct indicator of any problems that occurred during the deployment of Apex scripts.