caldav-mcp

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caldav-mcpYour calendar, over the open standard

MCP server for CalDAV calendars: events, tasks and journal entries

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  • One protocol, most calendars

    CalDAV is the standard behind Nextcloud, Radicale, Baikal, Fastmail, mailbox.org and iCloud, so one server reaches all of them. It walks from the URL you paste to the calendars behind it the way a real client does — a server root or a single collection URL both work — and reports what each calendar accepts.

  • Recurring events, expanded here

    A weekly meeting comes back as its individual occurrences, each with an id of its own, so one of them can be moved without touching the rest. The expansion happens in this server rather than being asked of the calendar, because support for that is uneven and fails silently — and it means a 09:00 meeting stays at 09:00 when the clocks change.

  • Only the tools you want

    CALDAV_READ_ONLY=true registers the read tools and nothing else. CALDAV_ALLOW_TOOLS cuts finer — essential for a curated handful, your own comma-separated list, or a whole family with list_* — and CALDAV_DENY_TOOLS subtracts. Whatever is filtered out does not exist on the protocol rather than failing when called, and a name that matches no tool stops the server at startup instead of quietly going missing.

  • A person is asked, not just told

    The destructive tools ask a person first, through MCP elicitation — a dialog the model cannot answer on its behalf, falling back to a server-issued token bound to the exact target where the client cannot show one. Upstream content is marked untrusted, and read-only mode simply does not register the write tools.

How caldav-mcp connects an MCP client to a CalDAV serverAn MCP client speaks stdio to caldav-mcp, which speaks WebDAV over HTTPS to a CalDAV server. Answers come back marked as untrusted calendar content.MCP clientClaude, Codex, …caldav-mcp22 toolsasks a personCalDAVRadicale, Baikal, Nextcloud, …stdioHTTPSPROPFIND · REPORT · PUTiCalendar, marked untrusted
caldav-mcp speaks MCP over stdio to the client and WebDAV over HTTPS to the calendar. Nothing it reads is treated as an instruction.

Running it elsewhere ​

A client that cannot spawn a local process — ChatGPT connectors, Claude on the web, Cursor, LibreChat — cannot start caldav-mcp the way Claude Code does. mcp-hub is the bridge: one container serves many stdio MCP servers over Streamable HTTP, with an OAuth 2.1 login behind a single password and long-lived tokens for the clients that cannot do OAuth. Its /hub endpoint puts every server behind six meta-tools, so one connector reaches all of them without N×tool schemas in the model's context, and it speaks both protocol revisions — a question this server asks travels through it to the person at the far end instead of ending at the gateway.

Its configuration is Claude Code's mcpServers format, so the entry you already have is the entry it takes: Through mcp-hub.

Released under the MIT License.

Copyright © 2026 Willi Thiel