AnkiMCP Server (Addon)

An Anki addon that exposes your collection to AI assistants via the Model Context Protocol (MCP).

What is this?

AnkiMCP Server runs a local MCP server inside Anki, allowing AI assistants like Claude to interact with your flashcard collection. This enables AI-powered study sessions, card creation, and collection management.

Part of the ankimcp.ai project.

Note on First Run

On first run, this addon downloads pydantic_core (~2MB) from PyPI. This is required because pydantic_core contains platform-specific binaries (Windows/macOS/Linux) that cannot be bundled in a single addon file.

Features

• Local HTTP server - Runs on http://127.0.0.1:3141/ by default
• Remote tunnel - Access your collection from anywhere via a public HTTPS URL
• MCP protocol - Compatible with any MCP client (Claude Desktop, etc.)
• Auto-start - HTTP server starts automatically when Anki opens
• Tunnel-friendly - Works with Cloudflare Tunnel, ngrok, or the built-in tunnel (exposing the HTTP server this way also requires extending the allowed hosts/origins)
• DNS-rebinding protection - The HTTP server validates Host/Origin headers against a loopback allowlist by default; extend it for tunnel/reverse-proxy exposure
• Optional API key - Require an Authorization: Bearer token on the HTTP transport via http_api_key (AnkiConnect-style; empty = disabled)
• Toolbar indicator - A ● AnkiMCP item in the top toolbar shows tunnel connection state at a glance (opt out via show_toolbar_indicator)
• Diagnostic logging - Opt-in log_to_file writes a rotating, secret-redacted log to user_files/ankimcp.log, with Open log folder / Copy diagnostics buttons in settings
• Field management - Add, rename, and reposition note-type fields via the model_fields tool (with an opt-in destructive remove)
• Cross-platform - Works on macOS, Windows, and Linux (x64 and ARM)

Installation

From AnkiWeb (recommended)

1. Open Anki and go to Tools → Add-ons → Get Add-ons...
2. Enter code: 124672614
3. Restart Anki

From GitHub Releases

1. Download anki_mcp_server.ankiaddon from Releases
2. Double-click to install, or use Tools → Add-ons → Install from file...
3. Restart Anki

NixOS

With flakes (recommended)

Add the flake input and use the pre-built package:

# flake.nix
{
  inputs.anki-mcp.url = "github:ankimcp/anki-mcp-server-addon";

  outputs = { nixpkgs, anki-mcp, ... }: {
    # Option A: Standalone — Anki with the addon pre-installed
    environment.systemPackages = [
      anki-mcp.packages.${system}.default
    ];

    # Option B: Composable with other addons via overlay
    nixpkgs.overlays = [ anki-mcp.overlays.default ];
    environment.systemPackages = [
      (pkgs.anki.withAddons [ pkgs.ankiAddons.anki-mcp-server ])
    ];
  };
}

Without flakes

# configuration.nix
{ pkgs, ... }:
let
  python3 = pkgs.python3;

  ankiMcpPythonDeps = python3.withPackages (ps: with ps; [
    mcp pydantic pydantic-settings starlette uvicorn anyio httpx websockets
  ]);

  anki-mcp-server = pkgs.anki-utils.buildAnkiAddon (finalAttrs: {
    pname = "anki-mcp-server";
    version = "0.20.0";
    src = pkgs.fetchFromGitHub {
      owner = "ankimcp";
      repo = "anki-mcp-server-addon";
      rev = "v${finalAttrs.version}";
      hash = ""; # nix will tell you the correct hash on first build
    };
    sourceRoot = "${finalAttrs.src.name}/anki_mcp_server";
  });

  ankiWithMcp = pkgs.anki.withAddons [ anki-mcp-server ];

  ankiWrapped = pkgs.symlinkJoin {
    name = "anki-with-mcp";
    paths = [ ankiWithMcp ];
    nativeBuildInputs = [ pkgs.makeWrapper ];
    postBuild = ''
      wrapProgram $out/bin/anki \
        --prefix PYTHONPATH ':' "${ankiMcpPythonDeps}/${python3.sitePackages}"
    '';
  };
in
{
  environment.systemPackages = [ ankiWrapped ];
}

Usage

The server starts automatically when you open Anki. Check status via Tools → AnkiMCP Server Settings...

Connect with Claude Desktop

Requires Node.js installed. Add to your Claude Desktop config (~/Library/Application Support/Claude/claude_desktop_config.json on macOS):

{
  "mcpServers": {
    "anki": {
      "command": "npx",
      "args": ["mcp-remote", "http://127.0.0.1:3141"]
    }
  }
}

Note: Claude Desktop doesn't natively support HTTP servers in its JSON config — mcp-remote bridges the connection via stdio.

Connect with Claude Code

claude mcp add anki --transport http http://127.0.0.1:3141/

Opencode

opencode mcp add anki --url http://127.0.0.1:3141/

Tunnel (Remote Access)

The built-in tunnel gives your Anki collection a public HTTPS URL, so AI assistants can reach it from anywhere — no port forwarding or reverse proxy needed. The collection is relayed through a WebSocket tunnel server (wss://tunnel.ankimcp.ai by default). Requires an ankimcp.ai account to log in.

How to connect:

1. Open Tools -> AnkiMCP Server Settings...
2. Click Connect Tunnel
3. If not logged in, a login dialog appears — it shows a one-time code; click Open Browser and enter that code at the verification URL (OAuth 2.0 device flow)
4. Once connected, a public tunnel URL is displayed (e.g., https://tunnel.ankimcp.ai/e3439277-9d1e-47a1-b961-d193a4590da0)
5. Use this URL in your AI client instead of http://127.0.0.1:3141

Using with Claude Desktop:

Replace the localhost URL with your tunnel URL in the Claude Desktop config:

{
  "mcpServers": {
    "anki": {
      "command": "npx",
      "args": ["mcp-remote", "https://tunnel.ankimcp.ai/<your-tunnel-id>"]
    }
  }
}

Using with Claude Code:

claude mcp add anki --transport http https://tunnel.ankimcp.ai/<your-tunnel-id>

Disconnect vs. Logout:

• Disconnect closes the tunnel connection. Credentials stay on disk — next Connect reconnects without re-login.
• Logout deletes credentials. Next Connect triggers the login dialog again.

Tunnel config fields (for advanced users / self-hosters):

• tunnel_server_url — WebSocket URL of the tunnel relay server (default: wss://tunnel.ankimcp.ai)
• tunnel_client_id — OAuth client identifier (default: ankimcp-cli)

Credentials are stored in the addon's own user_files/credentials.json (preserved across addon updates). They are not shared with the AnkiMCP CLI — the CLI keeps its own credentials under ~/.ankimcp/, so you log in to the addon and the CLI independently. The on-disk format is identical between the two.

Configuration

Edit via Anki's Tools → Add-ons → AnkiMCP Server → Config:

{
  "http_enabled": true,
  "http_port": 3141,
  "http_host": "127.0.0.1",
  "http_path": "",
  "http_allowed_hosts": [],
  "http_allowed_origins": [],
  "http_api_key": "",
  "cors_origins": [],
  "cors_expose_headers": ["mcp-protocol-version"],
  "disabled_tools": [],
  "enabled_destructive_tools": [],
  "max_notes_per_batch": 100,
  "tunnel_server_url": "wss://tunnel.ankimcp.ai",
  "tunnel_client_id": "ankimcp-cli",
  "media_import_dir": "",
  "media_allowed_types": [],
  "media_allowed_hosts": [],
  "show_toolbar_indicator": true,
  "log_to_file": false
}

HTTP Server Toggle

The http_enabled setting controls whether the local HTTP server runs. When set to false, the HTTP server won't start — only the tunnel transport is available. Default is true.

{
  "http_enabled": false
}

This is useful if you only use the tunnel and don't want a local HTTP server listening.

Toolbar Status Indicator

A persistent ● AnkiMCP item in Anki's top toolbar shows tunnel connection state (grey = off, amber = connecting, green = connected); clicking it opens the settings dialog. It's shown by default. Set show_toolbar_indicator to false to hide it (takes effect after an Anki restart).

{
  "show_toolbar_indicator": false
}

Diagnostic File Logging

Set log_to_file to true to write a rotating log to user_files/ankimcp.log (~1 MB per file, 3 backups). It's off by default. When enabled, the addon records a startup diagnostics snapshot (addon/Anki/Qt/Python versions plus the live provenance of shared libraries like pydantic, mcp, protobuf, etc.), which is the key data for diagnosing cross-add-on conflicts. Secrets — the http_api_key, OAuth tokens, and any Bearer token — are redacted before anything is written to disk.

{
  "log_to_file": true
}

The settings dialog (Tools → AnkiMCP Server Settings…) has an Open log folder button and a Copy diagnostics button (the same snapshot, formatted for pasting into a forum post). Takes effect after an Anki restart.

Disabling Tools

Hide specific tools or actions from AI clients to reduce token usage:

{
  "disabled_tools": [
    "sync",
    "card_management:bury",
    "card_management:unbury"
  ]
}

• "tool_name" — disables the entire tool
• "tool_name:action" — disables a specific action within a multi-action tool

Disabled tools are removed from the MCP schema entirely — AI clients never see them. Typos in tool/action names will produce console warnings.

Destructive Tools (Opt-In)

Tools or actions classified as destructive (high-risk operations) are hidden from AI clients by default. To expose them, add them to the enabled_destructive_tools allow-list:

{
  "enabled_destructive_tools": [
    "some_destructive_tool",
    "some_tool:destructive_action"
  ]
}

• "tool_name" — opts in an entire destructive tool
• "tool_name:action" — opts in a destructive action within a multi-action tool (a whole-tool entry does not implicitly opt in its destructive actions)
• disabled_tools still applies on top — an opted-in tool can still be disabled
• Entries that don't match anything, or match a non-destructive tool/action, produce console warnings

This is server-side enforcement: until opted in, destructive tools are absent from the MCP schema, so even a misbehaving client cannot call them. No currently shipped tool is destructive — this mechanism exists for future high-risk tools (e.g., deck deletion).

Custom Path

Set http_path to serve the MCP endpoint under a custom path. Useful when exposing Anki via a tunnel (Cloudflare, ngrok) to avoid a fully open endpoint:

{
  "http_path": "my-secret-path"
}

The server will be accessible at http://localhost:3141/my-secret-path/ instead of the root. Leave empty for default behavior.

Note: A custom path alone is not enough to expose the HTTP server through a tunnel or reverse proxy. You must also populate http_allowed_hosts/http_allowed_origins, or requests are rejected (421 for a non-loopback Host, 403 for a non-loopback Origin) — see Allowed Hosts and Origins (DNS-Rebinding Protection).

Security

The local HTTP server accepts requests only from loopback Host/Origin values by default, so ordinary local use needs no setup — localhost clients work out of the box. The sections below cover the available hardening layers (DNS-rebinding allowlist, optional API key, CORS, and media-import validation) for when you expose the server beyond your machine.

Upgrading from ≤ 0.20.0: if you reach the server through a tunnel, reverse proxy, or by binding to 0.0.0.0, requests now arrive with a non-loopback Host and are rejected with 421 until you allowlist that host — see Allowed Hosts and Origins (DNS-Rebinding Protection). (Browser clients additionally need their Origin allowlisted, otherwise 403.) Plain localhost setups are unaffected.

Allowed Hosts and Origins (DNS-Rebinding Protection)

The HTTP server enables DNS-rebinding protection with a built-in loopback allowlist (127.0.0.1, localhost, [::1]), so ordinary localhost clients work out of the box. If you expose the HTTP server through a tunnel or reverse proxy (e.g. ngrok, Cloudflare), requests arrive with a non-loopback Host (rejected with 421) — and, for browser clients, a non-loopback Origin (rejected with 403) — unless you extend the allowlist:

{
  "http_allowed_hosts": ["myapp.ngrok.io", "myapp.ngrok.io:443"],
  "http_allowed_origins": ["https://myapp.example"]
}

• http_allowed_hosts — Host-header values without a scheme (e.g. "myapp.ngrok.io" or "myapp.ngrok.io:443")
• http_allowed_origins — full origins with a scheme (e.g. "https://myapp.example")

Both lists are appended to the built-in loopback defaults (the defaults are not replaced). Changing these requires an Anki restart, consistent with the other http_* settings.

DNS-rebinding vulnerability reported by avishaigo-commits.

API Key (Optional HTTP Auth)

http_api_key adds an optional shared-secret auth layer on top of the HTTP transport (AnkiConnect-style). It is empty by default, which disables the layer and leaves the default behavior unchanged. When set to a non-empty value, every HTTP request must send an Authorization: Bearer <key> header matching that value, or it is rejected with 403:

{
  "http_api_key": "a-long-random-secret-key"
}

Configure your client to send the header. With Claude Code:

claude mcp add anki --transport http http://127.0.0.1:3141/ --header "Authorization: Bearer a-long-random-secret-key"

With mcp-remote (e.g. Claude Desktop):

{
  "mcpServers": {
    "anki": {
      "command": "npx",
      "args": [
        "mcp-remote",
        "http://127.0.0.1:3141",
        "--header",
        "Authorization: Bearer a-long-random-secret-key"
      ]
    }
  }
}

Notes:

• HTTP-only. The key applies only to the local HTTP transport. The tunnel does its own OAuth login and is unaffected by http_api_key.
• Complementary, not a replacement. It sits alongside DNS-rebinding protection (Allowed Hosts and Origins) — it does not replace it. Both layers apply independently.
• Pairs naturally with http_path + http_allowed_hosts when exposing the HTTP server through a tunnel or reverse proxy: a secret path obscures the endpoint, the allowlist permits the proxy host, and the API key authenticates each request.
• Use a long, random key (at least 16 characters). Leading/trailing whitespace is stripped from the presented token, so a configured key with surrounding whitespace will never match.
• Changing this requires an Anki restart, consistent with the other http_* settings.

CORS Configuration

To allow browser-based MCP clients (like web-hosted MCP Inspector), add allowed origins:

{
  "cors_origins": ["https://inspector.example.com", "http://localhost:5173"]
}

Use ["*"] to allow all origins (not recommended for production).

Note: A browser origin allowed via cors_origins must also be added to http_allowed_origins. CORS and the DNS-rebinding allowlist are separate layers: even with CORS configured, a non-loopback Origin is rejected with 403 by DNS-rebinding protection unless it is in http_allowed_origins.

The cors_expose_headers setting controls which response headers browsers can read. The default (mcp-protocol-version) lets browser-based MCP clients negotiate the protocol version. Since v0.16.0 the server runs in stateless mode, so mcp-session-id is no longer emitted and no longer needs to be exposed.

Media Security

Thanks to Hideaki Takahashi (Columbia University) for responsibly disclosing the media path traversal vulnerability.

The store_media_file tool validates all inputs to prevent path traversal and SSRF attacks:

• File paths are restricted to media files only (images, audio, video) via MIME type checking
• URLs must use http:// or https:// and cannot target private/internal networks
• Filenames are sanitized to remove path traversal sequences

Optional hardening via config:

{
  "media_import_dir": "/Users/me/anki-media",
  "media_allowed_types": ["application/pdf"],
  "media_allowed_hosts": ["192.168.1.50", "my-nas.local"]
}

• media_import_dir — restrict file path imports to this directory tree (empty = no restriction)
• media_allowed_types — allow additional MIME types beyond image/audio/video
• media_allowed_hosts — allow specific hosts to bypass private network blocking

Available Tools

Essential Tools

FSRS Tools

GUI Tools

These tools interact with Anki's user interface:

Resources

Prompts

Requirements

• Anki 25.07 or later (ships Python 3.13)
• Anki 25.02 and earlier ship Python 3.9, which is not supported — the MCP SDK requires Python 3.10+ (#8)

Architecture

The addon runs an MCP server in a background thread with two independent transports: local HTTP (FastMCP + uvicorn) and remote tunnel (WebSocket relay with in-memory transport). Both share the same FastMCP server instance. All Anki operations are bridged to the main Qt thread via a queue system, following the same proven pattern as AnkiConnect.

For details, see Anki Add-on Development Documentation.

Development

Running E2E Tests

E2E tests run against a real Anki instance in Docker using headless-anki.

# Install test dependencies
python -m venv .venv
source .venv/bin/activate
pip install -r requirements-dev.txt

# Build the addon
./package.sh

# Start Anki container
cd .docker && docker compose up -d && cd ..

# Run tests (waits for server automatically)
pytest tests/e2e/ -v

# Stop container
cd .docker && docker compose down

Or use the Makefile shortcuts:

make e2e        # Build, start container, run tests, stop
make e2e-up     # Just start container
make e2e-test   # Just run tests
make e2e-down   # Just stop container

CI

E2E tests run automatically on push to any branch and on PRs to main. See .github/workflows/e2e.yml.

License

AGPL-3.0-or-later

Links

• ankimcp.ai - Project homepage
• MCP Protocol - Model Context Protocol specification
• Anki Add-on Docs - Official Anki addon development documentation