you're not wrong and trimming context is legitimately the first thing that everyone should do. even with context trimming and a tight prompt the model still makes judgement calls about which tools to use and when to stop.
that's fine 90% of the time... the state machine for the other 10% where the model's judgement call costs you an hour of debugging later (confidently fixed wrong, or overzealously) or stops a mostly automated thing because it got stuck on the wrong path.