When should I reach for a log, a trace, or a metric? I hit that question constantly when I instrument code, and I watch coding agents hit it too. It sounds like it should be obvious. Errors, traces, logs, and metrics are the four kinds of telemetry most apps run on, four tools in one box, and they overlap enough that the honest answer is every developer’s favourite: it depends. You can stuff context into span attributes instead of logging it. You can count log events instead of emitting a metric.