Get Mcp Retention

Weekly retention for MCP users: who comes back and what they do.

A user's cohort is the ISO week of their first-ever MCP call (computed over full history, not the requested window, so a long-time user active this week is classified as returning rather than new). "New" always means first_call_at >= start_date, in the weekly split, the newUsers summary, and the cohort grid alike. The window bounds everything else: the weekly new/returning split, the cohort grid (share of each in-window cohort active 0..N weeks after its first call), and the per-user behavior rows (active weeks/days, 5-minute-gap sessions, calls, top tools, top schemas). Week-1 retention only counts cohorts whose week-1 window is fully inside the range, so a partial current week doesn't bias it low. Calls to retired tool names (always ok=false) are excluded — a stale client erroring against a renamed tool isn't engagement.