Is it safe to give Claude access to your calendar?
Giving Claude your calendar means handing a token to a service run by one person, which is me. This article lists what that token can do, what Calnio keeps about it, what Calnio cannot control, and how to take it back. I write the code and run the server, so read it knowing that.
3 min read
What the address can do
Anyone who holds the address can read every calendar in your Apple account and add, change or delete events in any of them. It reaches nothing else: no mail, no contacts, no files and no Notion pages. It cannot change a repeating event or one with guests.
The address is the password. The token sits in its path, so a copy left in a chat, a screenshot or a note works for whoever finds it.
What Calnio stores about it
The token is shown once. Calnio keeps its SHA-256 hash, its first 8 characters so you can tell addresses apart, and the times it was made and last used. A copy of the database cannot be used to call the API.
Every call is logged for 90 days: your account, whether it came through the connector or a script, what it did (list, add, change or delete), the time and whether it worked. The log holds no event, no calendar and no title. Calnio also strips the token from its own server logs.
The privacy policy lists this under API token.
What stays outside my hands
What Claude reads from your calendar goes to Anthropic, under the terms of your Claude plan. Calnio sends your calendar nowhere by itself and cannot see what Claude does with it afterwards.
Claude's custom connector page, read on 3 November 2026, warns that a custom connector reaches a service Anthropic has not verified. For this one, that means judging me. I run Calnio alone on a server I host, and the code is not open source, so you cannot read it. What you can check is the privacy policy and the Last used time in the Apple Calendar MCP window under Connections.
Limits already in place
An address allows 60 requests a minute. That caps a runaway client at 60 changes a minute. It does not stop it.
The delete tool is marked destructive, which makes a client that asks before risky steps ask first. An address has no read-only mode and no way to limit it to one calendar today. If either matters to you, the safe setting is no address at all.
How to turn it off
Open Connections, press the Apple Calendar MCP tile and press Turn off access. Create a new address does the same to the old one at once, so use it when an address may have leaked.
To cut Calnio off from iCloud itself, disconnect Apple Calendar in Calnio or revoke the app-specific password at account.apple.com. Changing your Apple Account password revokes every app-specific password, and the sync stops until you make a new one.