Good agencies report in leads and cost-per-lead against agreed targets; weak ones report in impressions, clicks, and 'engagement'. Activity metrics that always look busy. If you can't state your CPL from their last report, the report is decoration.
The monthly questions that keep everyone honest: What did we spend? How many leads? What did each cost? What did we learn and change? A competent agency answers in ten minutes with numbers you can verify in accounts you own.
Fair judgment also needs fair clocks. Paid search shows truth in ~60 days, SEO in ~6 months. Judge each channel on its native timeline, but never accept timeline as a reason for measurement not existing.