NextDNS MCP Server

A Model Context Protocol (MCP) server for the NextDNS API, built with FastMCP and a small set of grouped CRUD tools.

Overview

This project provides an MCP server that exposes NextDNS API operations as tools that can be used by AI assistants and other MCP clients. The server registers a small set of domain-grouped CRUD tools directly; it does not generate tools from an OpenAPI spec.

Features

• Domain-grouped CRUD tools exposing the full NextDNS API surface through ~8 high-level tools
• Profile Management: Full CRUD operations - create, read, update, and delete profiles
• Profile Access Control: Fine-grained read/write restrictions per profile, with read-only mode support
• DNS-over-HTTPS Testing: Perform DoH lookups to test DNS resolution through profiles
• Settings Configuration: Comprehensive grouped settings management including logs, block page, and performance
• Logs: Query log retrieval, download, and clearing
• Analytics: Comprehensive DNS query analytics and statistics, including time-series and plotting
• Content Lists: Manage denylist, allowlist, privacy blocklists, native tracking, security TLDs, and parental control
• Security: Complete security settings and TLD blocking configuration
• Privacy: Privacy settings, blocklists, and native tracking protection management
• Parental Control: Settings management with safe search and YouTube restrictions
• Reference OpenAPI spec: The bundled nextdns-openapi.yaml documents the NextDNS API surface for validation tooling
• Docker Support: Containerized deployment with proper OCI labels
• Safety Mechanisms: Write operation protections and validation

Documentation

Complete documentation can be found in docs/index.md.

Quick Start

Prerequisites

• Python 3.12+
• uv (for development)
• Docker (for containerized deployment)
• NextDNS API key (get one here)

Configuration

1. Copy the .env.example file to .env:

   cp .env.example .env

2. Edit .env and set your NextDNS API key:

   NEXTDNS_API_KEY=your_api_key_here
   NEXTDNS_DEFAULT_PROFILE=your_profile_id  # Optional
   NEXTDNS_TEST_PROFILE=test_profile_id     # For write operation tests
   
   # Optional: Profile access control (see Profile Access Control section)
   # NEXTDNS_READABLE_PROFILES=profile1,profile2
   # NEXTDNS_WRITABLE_PROFILES=test_profile
   # NEXTDNS_READ_ONLY=false

Running with Docker

1. Build the Docker image:

   docker build -t nextdns-mcp:latest .

2. Run the container with environment variables:

   Option A: Direct environment variables (simple)

   docker run -i --rm \
     -e NEXTDNS_API_KEY=your_api_key_here \
     -e NEXTDNS_DEFAULT_PROFILE=your_profile_id \
     nextdns-mcp:latest

   Option B: Docker secrets (recommended for production)

   # Create secret
   echo "your_api_key_here" | docker secret create nextdns_api_key -
   
   # Run with Docker Swarm
   docker service create \
     --name nextdns-mcp \
     --secret nextdns_api_key \
     -e NEXTDNS_API_KEY_FILE=/run/secrets/nextdns_api_key \
     nextdns-mcp:latest

   Or for non-swarm (using mounted file):

   # Create a secret file
   echo "your_api_key_here" > /tmp/api_key.txt
   chmod 600 /tmp/api_key.txt
   
   # Run with mounted secret
   docker run -i --rm \
     -v /tmp/api_key.txt:/run/secrets/nextdns_api_key:ro \
     -e NEXTDNS_API_KEY_FILE=/run/secrets/nextdns_api_key \
     nextdns-mcp:latest

   Option C: Environment file (development)

   docker run -i --rm \
     --env-file .env \
     nextdns-mcp:latest

   Note: MCP servers use stdio (standard input/output) for communication, not HTTP ports.

   Alpine variant

   An Alpine Linux image is also available. To build it locally, use Dockerfile.alpine:

   docker build -f Dockerfile.alpine -t nextdns-mcp:alpine .

   The published Alpine tags use the -alpine suffix (e.g. nextdns-mcp:alpine, nextdns-mcp:2.0-alpine). The python:3.14-slim image remains the recommended default.

Running Locally (Development)

1. Install dependencies:

   uv sync

2. Run the server:

   uv run python -m nextdns_mcp.server

HTTP Transport (network access)

By default the server uses stdio, which is what MCP clients (Claude Desktop, CLI tools) expect. You can switch to a streamable-HTTP transport for network-based clients, but the HTTP endpoint has no built-in authentication.

Variable	Default	Description
MCP_TRANSPORT	stdio	Set to http to serve over streamable-HTTP
MCP_HOST	127.0.0.1	Interface to bind. Loopback-only by default
MCP_PORT	8000	Port to listen on

Because there is no authentication, the default bind is loopback-only (127.0.0.1). This means the HTTP endpoint is only reachable from the same host, which is safe for local development and same-host proxies.

In HTTP mode the server also serves GET /health, a readiness check that probes the NextDNS API with the configured key: it returns 200 only when the credentials work, and 503 with a failure class (auth or unreachable) when they do not. See the FAQ.

Binding to a non-loopback interface (explicit opt-in)

To make the endpoint reachable from other hosts you must explicitly set MCP_HOST to a non-loopback address (e.g. 0.0.0.0 or a specific IP). The server logs a prominent SECURITY warning on startup when this happens, because it exposes every tool — and the full reachability of your NextDNS API key — to anyone who can reach the port.

A non-loopback bind is only production-suitable when it is fronted by a reverse proxy (or gateway) that provides authentication and/or TLS, such that unauthenticated remote callers cannot reach the /mcp endpoint. Recommended setup:

• Terminate TLS at the reverse proxy.
• Require authentication (e.g. a shared secret, OAuth2/OIDC, or IP allow-listing) before forwarding to the MCP server.
• Bind the MCP server itself to a private interface or 127.0.0.1 behind the proxy where possible.

# Loopback-only (default, safe for local use):
MCP_TRANSPORT=http uv run python -m nextdns_mcp.server

# Non-loopback bind — MUST be placed behind an authenticating reverse proxy:
MCP_TRANSPORT=http MCP_HOST=0.0.0.0 uv run python -m nextdns_mcp.server

Architecture

This server uses a modern, declarative approach:

1. OpenAPI Specification (nextdns-openapi.yaml): Complete NextDNS API documentation
2. FastMCP Foundation: Server built from grouped CRUD tools registered in src/nextdns_mcp/tools/; the OpenAPI spec is a reference for validation only (issues #141/#146)
3. HTTP Client: Authenticated httpx.AsyncClient with profile-level access control for NextDNS API calls
4. MCP Protocol: Tools, resources, and prompts exposed via Model Context Protocol

Key Components

• src/nextdns_mcp/nextdns-openapi.yaml: OpenAPI 3.0 specification for NextDNS API (reference/validation only); a Spectral lint workflow (openapi-lint.yml) enforces explicit per-operation security declarations via spectral.yaml, runnable locally with npx @stoplight/spectral lint -r spectral.yaml src/nextdns_mcp/nextdns-openapi.yaml
• src/nextdns_mcp/server.py: FastMCP server implementation
• Dockerfile: Container definition with OCI labels for container metadata
• AGENT.md: Development guidelines and safety rules

Docker Tags

This project publishes official Docker images with a standardized tagging policy. The default image is based on python:3.14-slim; an Alpine Linux variant is also available and tagged with an -alpine suffix.

Primary (python:3.14-slim) tags

• :latest: Floating tag that tracks the most recent successful build from the main branch. This tag is rebuilt on changes to main and via scheduled rebuilds.
• :<major>: Floating tag for the most recent build in a given major series (e.g., :2). This tag is updated whenever a new image for that major line is published and may include unreleased changes if the corresponding build comes from a branch head.
• :<major>.<minor>: Floating tag for the most recent build in a given minor series (e.g., :2.0). Like :<major>, it is updated when new images are built for that series and may include unreleased changes.
• :<major>.<minor>.<patch>: Tags for specific application releases (e.g., :2.0.3). These are intended to be immutable once published via the release workflow.

Alpine tags

• :alpine: Floating tag for the most recent Alpine build from main.
• :<major>-alpine: Floating tag for the most recent Alpine build in a major series (e.g., :2-alpine).
• :<major>.<minor>-alpine: Floating tag for the most recent Alpine build in a minor series (e.g., :2.0-alpine).
• :<major>.<minor>.<patch>-alpine: Specific Alpine release tag (e.g., :2.0.3-alpine).

All floating tags (:latest, :<major>, :<major>.<minor> and their -alpine counterparts) are rebuilt regularly to include the latest OS security updates and any application changes present in the source commit used for that build. Consumers who require strict version pinning should use the full :<major>.<minor>.<patch> or :<major>.<minor>.<patch>-alpine tags.

License

This project is released under the MIT License.

Contributing

1. See AGENT.md for guidelines and architecture
2. Note that NextDNS does not provide an OpenAPI specification. This is based on their documentation and may not reflect the current state of the API.