English | Deutsch | Français

MCP Connector for Nextcloud

A curated MCP server that connects your Nextcloud (files, calendar, notes, Deck, contacts, Tables, Talk and Mail) to AI assistants such as Claude, Cursor, ChatGPT or your own agents. Installed as a Nextcloud ExApp, it is its own OAuth 2.1 authorization server as well.

Findling + Nextcloud MCP Connector = the retrieval layer for your own RAG. Findling makes the content of your documents searchable, scans included. The connector hands those hits to any MCP client, with exactly the rights of the asking user; measured in tests/integration/test_content_hit_fidelity.py. You bring the model, and no content leaves your server.

What it does

• 23 tools across nine app families: files, calendar, notes, Deck, contacts, Tables, Talk, Mail and cloud wide search
• OAuth 2.1 to the MCP authorization specification: dynamic client registration, PKCE S256, audience bound tokens, refresh rotation with reuse detection and immediate revocation. Claude.ai and ChatGPT are given one URL and never see a password or an app password
• Every request runs with the rights of the signed in user, so Nextcloud permissions apply unchanged and the assistant never sees more than you do
• Per user management: every account pauses or resumes its own access and disconnects a single assistant, on this app’s connections page under Settings, Security, MCP Connector
• prepare_context bundles a search, the coming week of events, the waiting Talk conversations and the unread mail counts into one call, each source with its own time budget
• A deliberately small tool set, so this server fits next to your other MCP servers even in clients with a hard tool limit
• No cron, no indexing, no telemetry, no copy of your data, and no credential is ever logged

What this server cannot do

• No deleting: no tool issues a DELETE against files, events, notes, cards or contacts
• No overwriting: writes are create-only, and files_upload refuses an existing path with a clear error instead of replacing it
• No user-visible moving or renaming, no share changes and no permission changes; binary uploads use Nextcloud’s private chunk assembly and still refuse an existing destination
• Mail is strictly read only: no sending, no draft, no move, no flag, no delete, and no attachment download
• No admin access: the server acts as one user and inherits exactly that user’s permissions
• No full text search inside file contents unless a search app such as Findling is installed

That is a design constraint and not a promise of good behaviour: a contract test reads the modules and fails on the first destructive call, tests/contract/test_no_destructive_calls.py.

Tools

read means the tool only reads, create-only means it can create new objects but never modifies or removes existing ones. The table is not maintained by hand: a contract test reads the live registry and fails if a name or a level disagrees with it.

search and fetch exist because the ChatGPT connector profile requires exactly these two names and schemas. They are thin wrappers over the tools above, not a second implementation.

An answer of unified_search, with both honest cases in it: a hit whose id the read tools resolve, and a provider whose entries stay a URL instead of an invented id. A provider that fails or stalls is named under degraded, so a partial answer is visibly partial. Notes, Deck, Tables, Talk and Mail are optional apps; the tool list stays the same everywhere and a missing app is answered in one sentence, never with an empty result.

{"query":"budget","count":2,"results":[{"id":"file:4711","title":"Budget 2026.md","url":"https://cloud.example.org/index.php/f/4711","provider":"files","kind":"file"},{"id":"url:https://cloud.example.org/index.php/call/abc123","title":"Khaled","url":"https://cloud.example.org/index.php/call/abc123","provider":"talk-conversations","kind":"url","resolvable":false}]}

Switching tool bundles off

• Variable: NC_MCP_DISABLED_TOOLS, comma separated bundle names, read at start.
• Where to set it: as a deploy environment variable of the ExApp, either in the deploy options of the install/update dialog, or on the command line: occ app_api:app:register mcp_connector --env "NC_MCP_DISABLED_TOOLS=mail,calendar" (unregister first on an existing installation; user connections survive, the container is recreated). The start log names the bundles that are off.
• Default: unset, every bundle is on.
• Example: export NC_MCP_DISABLED_TOOLS=mail,calendar, useful when a second MCP server already offers mail and calendar and a smaller model confuses the two.
• Bundles and their tools:
  • calendar: calendar_list_events, calendar_create_event
  • chatgpt: search, fetch
  • contacts: contacts_search
  • context: prepare_context
  • deck: deck_browse, deck_create_card
  • files: files_search, files_list, files_read, files_download, files_read_as_markdown, files_upload
  • mail: mail_browse
  • notes: notes_search, notes_read, notes_create
  • search: unified_search
  • tables: tables_browse, tables_create_row
  • talk: talk_browse, talk_send
• An unknown name, or every name at once, stops the server at start with a message that lists the valid names.
• Not an access control: search, fetch and prepare_context still reach the content of a switched off bundle. Use Nextcloud permissions, the kein-ki tag or NC_MCP_FILES_ROOT to keep content away from the assistant.
• ChatGPT connectors expect the chatgpt bundle (search, fetch).
• The ExApp declares the variable and logs at start which bundles are switched off.

Excluding folders: the kein-ki tag

Tag a folder or file with the collaborative tag kein-ki and the assistant no longer sees it or anything below it. Check the setup with php occ mcp_connector:exclusion:check --admin=. Most important limit: a tag above the root of a share does not protect the shared folder for the recipient, so tag the folder you share. Setup, all limits and the findings they rest on: docs/exclusion.md.

Security

This server holds private data, it takes in untrusted content (a mail or a Talk message is written by somebody else, and for a mail that somebody needs no account on your instance), and it has an outgoing channel, talk_send. Those three together are what Simon Willison calls the lethal trifecta, and a language model does not reliably separate data from instructions. So talk_send sits behind the administration switch NC_MCP_TALK_SEND, which closes the outgoing channel for the whole instance while reading stays untouched, and Mail adds reach with deliberately no way out of its own. Neither makes prompt injection impossible. The long form, with every countermeasure and the honest remainder, is in docs/privacy.md. The switches sit under Settings, Administration, Security:

Installation

Listed in the Nextcloud App Store as MCP Connector and installed as an ExApp: enable AppAPI, register a deploy daemon, then deploy and enable the app. Nextcloud 32 to 35. On 34.0.3 the apps management interface does this for you, on earlier versions occ is the reliable path. The walkthrough with the exact commands and the pitfalls that actually happen: docs/exapp-install.md.

Since 0.2.0 the server also runs without AppAPI. nc-mcp-oauth serves the same endpoint, authorization server and consent screen for a Nextcloud it reaches over HTTPS, and because no AppAPI header names the account behind a browser there, the consent decision is confirmed by the OIDC single sign-on Nextcloud already trusts. Setup, secrets and operation: docs/standalone-oauth.md.

Clients

Claude.ai and ChatGPT connect over OAuth with one URL. Claude Desktop, Claude Code, Cursor and other local clients run the same server over stdio, with a Nextcloud app password:

uv tool install nextcloud-mcp-connector

export NC_MCP_URL=https://cloud.example.com
export NC_MCP_USER=alice
export NC_MCP_APP_PASSWORD=xxxxx-xxxxx-xxxxx-xxxxx-xxxxx
# Optional: expose only this Nextcloud directory to file tools
export NC_MCP_FILES_ROOT=/Documents/AI

nc-mcp

The same server speaks Streamable HTTP for remote clients, on POST /mcp, where NC_MCP_ALLOWED_HOSTS is required in practice. Setup step by step, every environment variable and the three errors that actually happen: docs/client-setup.md. OAuth for administrators: docs/oauth-setup.md. Automation platforms are clients too, with one OAuth connection per person: docs/n8n-setup.md.

When NC_MCP_FILES_ROOT is set, / becomes that directory for the file tools. For example, /scan.pdf is resolved under /Documents/AI, and no file tool can reach its parent folders.

Privacy

Every call goes to your Nextcloud and returns: nothing runs in the background, no result is cached, no index is kept. In the HTTP modes the credentials travel per request and are never stored. Questions users ask: docs/faq.md.

Enterprise

The audit log is part of this app and not of an add-on. With it on, every tool call is written down with the account it ran for, the tool, the time, the calling app and the outcome, and never a parameter value or any part of a result. It is off by default, an administrator switches it on in the admin settings of this app, and the entries are read with occ mcp_connector:audit:read. Every entry is hash chained to the one before it, and occ mcp_connector:audit:verify walks the chains and names the first place one of them is broken.

Sign in through the identity provider your organisation already runs arrived with 0.2.0, in the deployment without AppAPI: the consent decision is confirmed by the OIDC single sign-on Nextcloud already trusts through user_oidc. A service of the organisation can also act in a user’s name with a token it exchanged at that provider, and the setup, the measured limits of the route and what is still open about it are in docs/token-exchange.md. Still planned on that road are group policies.

Request a quote: [email protected]

Development

uv sync
uv run pytest
uv run ruff check .
uv run ruff format --check .

uv run pytest starts nothing and needs nothing. uv run pytest -m matrix starts the HTTP server as a subprocess, uv run pytest -m integration needs the local test Nextcloud from compose.test.yml.

App id, package names and repository name are frozen, see docs/app-id-freeze.md.

Licence

AGPL-3.0-or-later, see LICENSE. Donations: PayPal and Stripe.