Stackdriver Trace is automatically enabled for all applications running on the App Engine standard environment. The App Engine standard environment application don't require any additional instrumentation libraries.
Applications on VMs or containers (including Compute Engine, App Engine flexible environment, Google Kubernetes Engine, and those running with other cloud providers or on-premises) should use client libraries to submit traces to the service. For these configurations, follow the setup guidance for your languages client library, or use the Stackdriver Trace API, to send traces to the service.
After deployment, you can view recorded traces and inspect the RPCs in your application.