The pull-side metrics transport: a Prometheus exposition on its own listener, never on the proxy's data port. A backend that scrapes selects it with OTEL_METRICS_EXPORTER=prometheus, which the SDK answers with a no-op push exporter, leaving the endpoint to the application. The exposition carries the whole OpenTelemetry resource, naming the host, the process, and any cloud or cluster identity the SDK detected, so it never shares the port untrusted registry clients reach and binds localhost until an operator widens it. OTEL_EXPORTER_PROMETHEUS_HOST and OTEL_EXPORTER_PROMETHEUS_PORT address it, as the OpenTelemetry specification defines them.