$ curl -X POST .../tools/account.usage/call -d '{"period":"7d"}'

{
  "period": "7d",
  "total_calls": 1,247,
  "total_cost_usd": 3.82,
  "cache_hit_rate": 0.67, // 67% served from cache
  "avg_latency_ms": 142,
  "top_tools": [
    { "tool": "crypto.get_price", "calls": 423, "cost": 0.42 },
    { "tool": "weather.current", "calls": 312, "cost": 0.31 },
    { "tool": "amadeus.flight_search", "calls": 89, "cost": 3.12 }
  ]
}