Connect n8n

With n8n you build workflows where an AI agent reads your calendars and creates events — across all connected providers at once: Google, Outlook, iCloud, GMX, WEB.DE and more. No single Google Calendar or Outlook node can do that.

The address (MCP server URL) you will enter below is:

https://app.kalender-sync.de/mcp

Prerequisites

• A Kalender Sync account with connected calendars — reading and creating events work on every plan, including Free.
• n8n version 2.19.0 or newer (Cloud or self-hosted). Older versions drop structured tool results — the agent then falsely claims your calendar list is empty. Find your version in n8n under Help → About.
• An access key from the app (step 1).

1. Create the access and key in Kalender Sync

In the app, open AI assistant → Connect the assistant and pick n8n. As with every access, you pick the calendars one by one and set the detail level per calendar — calendars you don’t share do not exist for n8n.

Create key gives you your access key (a token starting with ksa_). It is shown only once — copy it straight into the n8n credential (step 2). Treat it like a password: whoever holds the key holds exactly the access you gave this connection.

2. Build the workflow

The fast way: n8n’s AI builder

n8n can generate the workflow from a description. This template works:

Build a workflow with a Chat Trigger connected to an AI Agent.

The AI Agent should use an MCP Client Tool node with these settings:
- Endpoint URL: https://app.kalender-sync.de/mcp
- Server Transport: HTTP Streamable
- Authentication: Header Auth (I will fill in the credential myself)
- Include all available tools

Set the AI Agent's system message to:
"You are a calendar assistant with access to the user's calendars via
Kalender Sync MCP tools. Use list_calendars first to see which calendars
are available and their visibility levels. When asked about availability,
use get_availability. Always mention any warnings the tools return, and
say what your answer does NOT cover."

Use gpt-4.1-mini as the chat model.

The builder cannot create credentials — you enter the token by hand afterwards (next section, item 3).

The manual way: four nodes

1. Add a Chat Trigger (or any other trigger — see the workflow ideas below).
2. Add an AI Agent node behind it. As the chat model we recommend gpt-4.1-mini or a comparable non-reasoning model (see Troubleshooting for why).
3. Attach an MCP Client Tool node under the agent’s Tool slot:
   • Endpoint URL: https://app.kalender-sync.de/mcp
   • Server Transport: HTTP Streamable
   • Authentication: Header Auth → create a new credential:
     • Name: Authorization
     • Value: Bearer ksa_… (your token from step 1 — the word Bearer, one space, then the token)
   • Tools to include: All
4. Give the agent a system message — the one from the builder prompt above works verbatim.

Once everything is wired up, the MCP client node lists the available tools — list_calendars, get_availability, search_events and (with write access enabled) create_event, update_event, delete_event. Technical details for each tool: tool reference.

3. Test it

Open the chat and ask:

• “Which calendars do you see, and with which visibility?” — the agent should name exactly the calendars you shared in step 1, including their detail levels.
• “Am I free next Tuesday between 9 and 12?” — availability across all shared calendars.
• “Create ‘test event via n8n’ tomorrow at 10 in [calendar name]” (Basic and up, calendar with write access) — then: “Delete it again.”

Every call shows up in the access log on the AI assistant page — you can watch live which tool was called when.

Workflow ideas

Availability bot for Slack or Telegram. Slack/Telegram trigger → AI agent with Kalender Sync tools → reply in the channel. Colleagues (or you, from your phone) ask for free slots in plain language — the agent checks Google, Outlook and GMX in one call.

Event from a form. n8n form or webhook trigger (say, a booking request from your website) → the agent extracts date, time and topic → create_event in your work calendar. The agent only manages events it created itself — it can never touch your existing events.

Morning briefing. Schedule trigger (weekdays at 7) → the agent summarises your day with search_events and get_availability → email or Slack: “4 events today, biggest gap 1–3 pm.”

Conflict watchdog. Hourly schedule trigger → the agent checks get_availability for double bookings between work and personal calendars → messages you only when something overlaps.

Troubleshooting

“I don’t see any calendars” — although the tool calls succeed

In almost every case this is one of two n8n pitfalls, not your access:

1. n8n older than 2.19.0: its MCP client drops structured tool results, the agent receives an empty answer and calls the tool in a loop (n8n issue #26963). → Update n8n.
2. Reasoning model + streaming (e.g. gpt-5-mini with streaming enabled on the chat trigger): tool results arrive empty at the model. → Switch the model to gpt-4.1-mini or similar, or set the chat trigger’s response mode from “Streaming” to “When Last Node Finishes”.

To check whether your access itself works, look at the access log in the app: if it shows successful list_calendars calls, the problem is in the workflow, not the access.

• 401 / “Unauthorized”: token mistyped, expired or revoked. Check the credential: header name exactly Authorization, value exactly Bearer ksa_… (with the space). If in doubt, create a fresh token in the app.
• Only SSE offered as transport: your n8n is older than 1.112. We only support HTTP Streamable — please update.
• A calendar is missing from the list: it isn’t shared with this access — add it in the app under AI assistant → Edit sharing. Changes apply immediately, no new token needed.
• create_event fails: write access is available on every plan and has to be enabled per calendar.

Security & control

The same rules as for every assistant access apply to n8n: you decide per calendar what is visible, every query is logged (never the content of your events), and revoking in Kalender Sync kills the token instantly — regardless of what is stored in n8n. Keep the token exclusively in n8n credentials, never in node parameters or expressions, so it cannot leak into execution logs.