The MCP connector stack

R21 runs agents against production systems, not sample data. This is the list of what is actually connected, and the count on the homepage is this list's length rather than a number someone typed.

The three tiers

They are not interchangeable, and the difference is who is trusted with what:

• Infrastructure R21 owns. Automation and anything needing an external trigger runs on n8n, on R21's own server. Hosting is Vercel, domains sit at Cloudflare, data on Supabase, mail through AWS SES.
• Systems R21 operates on a client's behalf — Stripe, Wix, Metricool, ClickUp, the Google surfaces. An agent reaching these is acting inside someone else's account, which is a different risk category from reading a repository.
• Reference and capability — Context7, Exa, NotebookLM, Playwright, Hugging Face. These bring information or ability in rather than reaching out to a system of record.

What "connected" is allowed to mean

Every entry here was observed connected in a live working session. That is a deliberately weak claim, honestly stated: it means the connector authenticated and answered, not that R21 uses all eighteen every week.

The temptation on a page like this is to list what is installed, which is always a longer and more impressive list, and always partly fiction. The rule this site is built on applies to its own stack page.

Make.com is not on this list, and the reason is measured

R21 migrated its automations off Make to self-hosted n8n through August 2026 — in stages rather than in one cutover. Eleven LeadNotify relays moved on 2026-08-06, taking active scenarios from 18 to 7; two more followed on 08-08.

The effect is the strongest number R21 has on the value of the move. Measured over a clean four-day window entirely after the migration, consumption fell to 8.5× below the pre-migration rate.

What is not claimed: a date on which Make was switched off. The last recorded reading, 2026-08-10, still showed five active scenarios, and no measurement after that has been taken. An earlier version of this page named a retirement date that nothing supports, and both R21's internal notes and this entry had settled on different wrong dates — which is the ordinary way an unrecorded fact becomes a confident one. It says what was measured, and stops.

Depth

Listed as partial rather than deep: this page gives the shape and the reasoning, not credentials, scopes or configuration. It previously claimed deep, which the spec defines as full method and reproducible config, and it never contained either.