Hetzner Cloud (unofficial)

the-real-hetzner-mcp

An unofficial local Model Context Protocol (MCP) server (stdio) for the Hetzner Cloud API: every operation of the vendored Hetzner Cloud API specification as a typed tool, read and write, plus hand-tuned wrappers for the common server operations. npm package: @mguttmann/hetzner-cloud-mcp.

Unofficial project. This server is not affiliated with, endorsed by, sponsored by or supported by Hetzner Online GmbH. "Hetzner" is a trademark of Hetzner Online GmbH. The vendored API specification (specs/cloud.spec.json) is Hetzner's and is not covered by this project's MIT License. See NOTICE.

Maintenance status

• Maintained on a best-effort basis by one maintainer (@mguttmann) in spare time. There is no support contract and no guaranteed response time.
• Security fixes take priority over features. Report vulnerabilities privately through GitHub private vulnerability reporting, never in a public issue; see SECURITY.md.
• Only the latest minor release gets fixes (SECURITY.md lists the supported versions).
• Dependency updates come from Dependabot; CI fails when a runtime dependency has a known high or critical advisory.
• Releases are built and published by GitHub Actions from a tag on main, with a CycloneDX SBOM, SHA256SUMS and build provenance (CHANGELOG.md lists the changes).
• Issues and pull requests are welcome. Tool names, parameters and environment variables are kept stable between releases; see AGENTS.md for the contract rules.

Features

• Full coverage of the Hetzner Cloud API via codegen from specs/cloud.spec.json (one generated tool per operation), plus hand-tuned wrappers for the common server operations. The exact tool list and count are pinned by tests/tools-contract.test.ts against tests/snapshots/tools-contract.json.
• hcloud_raw_request as a generic escape hatch for any endpoint.
• Capped 429 backoff, automatic pagination with a soft-cap, action polling with a wall-clock budget (see Timeouts and retries).
• Optional write guard HETZNER_CONFIRM_WRITES=true: every tool that is not read-only returns a preview (tool name and input) unless the call carries confirm: "YES".
• Optional operator switches HETZNER_READ_ONLY=true (only read-only tools and GET through hcloud_raw_request run) and HETZNER_DENY_TOOLS (tool name globs that always return an error). Both leave the tool list and the schemas unchanged.

Out of Scope

Not covered: Hetzner Robot (the dedicated-server API), Hetzner DNS (the standalone DNS product, a separate API from Cloud DNS) and Hetzner Storage Boxes. They are not part of the Cloud API and the codegen has no spec for them.

Covered: Cloud DNS zones and RRSets (/v1/zones) are part of the Cloud API spec, so they are in scope through the generated tools.

Installation

Requires Node.js 22.12 or newer (engines in package.json; the CI matrix in .github/workflows/ci.yml tests the floor and the current Node lines).

Do not install 0.1.x. npm versions below 0.2.0 (0.1.0 and 0.1.1) are affected by a path-injection vulnerability that is fixed in 0.2.0, see SECURITY.md.

From npm (0.2.0 or newer)

The package name is exactly @mguttmann/hetzner-cloud-mcp; packages with similar names are not from this project.

npm install -g "@mguttmann/hetzner-cloud-mcp@>=0.2.0"

The version range makes npm refuse the vulnerable 0.1.x versions. If npm reports that no matching version exists, 0.2.0 is not published yet: install from a pinned git commit instead. In your MCP client config the command is then just hetzner-cloud-mcp (no path needed).

With npx (no global install)

npx -y "@mguttmann/hetzner-cloud-mcp@>=0.2.0"

MCP clients start it the same way, see Variant C. Keep the version range: without it npx would take whatever version npm serves as latest.

From the MCP Registry

Once listed, the server is in the official MCP Registry as io.github.mguttmann/the-real-hetzner-mcp, with the npm package above as its package. Clients that install from the registry use the same npm package.

From a pinned git commit

git clone https://github.com/mguttmann/the-real-hetzner-mcp.git

cd the-real-hetzner-mcp git checkout npm ci npm run build

Pin a full commit SHA, not a branch name: the commit of the v0.2.0 tag (git rev-list -n 1 v0.2.0) or a later commit on main. npm ci installs exactly the committed lockfile.

Setup

With the npm package, set the variables in the env block of your MCP client configuration (see MCP Connector Setup); the package ships no .env file. In a git checkout:

cp .env.example .env

Add HETZNER_API_TOKEN to .env (Read & Write token from the Hetzner Cloud Console)

npm run refresh-spec and npm run generate are not part of the setup: they change the tool surface (see Spec Updates).

The server reads its configuration from the environment. At startup it also loads the .env file in the package directory (next to package.json, dotenv), never one from the current working directory; variables that are already set win. A deployment can pass the file explicitly instead, from any working directory: node --env-file=/path/to/.env dist/index.js.

Optional smoke test against the real API (four read-only calls):

npm run test:live

Configuration

Only HETZNER_API_TOKEN is required. The defaults below are pinned by tests/config.test.ts. A numeric value that is not a positive number, and an unknown boolean or log level, falls back to the default. Exceptions that stop the server at startup instead: an invalid HETZNER_API_BASE and an unknown HETZNER_READ_ONLY value.

Development only: RUN_LIVE_TESTS=1 enables tests/live-smoke.test.ts (set by npm run test:live), and HETZNER_LIVE_SMOKE_ANCHORS optionally names servers that test expects to find.

Timeouts and retries

Retries: a 429 is retried after Retry-After, or after a short backoff when the header is missing (Hetzner refills one request per second; RateLimit-Reset is the time the bucket is full again and is not used as a delay). A 5xx is retried with backoff, except for POST, which may already have been processed. With the defaults one tool call answers within about max(HTTP_TIMEOUT_MS, ACTION_POLL_TIMEOUT_MS) (tests/call-budget.test.ts measures this), so it stays below a 60 s client call timeout, common in MCP clients and gateways. Keep that relation if you raise the values. Auto-paginated lists run one request per page within PAGINATION_TIMEOUT_MS; when that budget ends, the pages read so far come back with truncated: true and a note, never as a list that looks complete.

When polling fails or the budget runs out after a successful write, the tool returns the write response (for example the new resource id and a one-time root_password) with polling_timed_out: true, plus polling_error if polling failed.

MCP protocol

The server speaks MCP over stdio only and opens no network port.

• Protocol revisions: a client that asks for 2024-11-05, 2025-03-26, 2025-06-18 or 2025-11-25 gets that revision back; a client that asks for a newer one (for example 2026-07-28) in initialize gets 2025-11-25 (tests/server.test.ts).
• 2026-07-28 is opt-in: with MCP_SERVE_MODERN_PROTOCOL=true the server also answers a client that opens with server/discover and serves it the 2026-07-28 revision, with the same tools. A client that opens with initialize still gets the 2025-era session above (tests/serve-protocol.test.ts). The default is false: a client in auto mode (such as the python mcp client) would switch to the new revision as soon as it is offered, so turn it on only after checking the client. See docs/adr/0001-mcp-sdk-v2.md.
• Message size limit: one inbound JSON-RPC message (one stdin line) may be at most 10 MiB, the MCP SDK's stdio limit (tests/transport-lifecycle.test.ts). A longer line closes the transport: the server logs mcp transport error on stderr and exits with code 1. Keep large arguments (for example user_data) well below that size. Outbound, a tool result is cut at MAX_OUTPUT_BYTES (at most 8 MiB, tests/output-cap.test.ts) and then ends with an [output truncated by MAX_OUTPUT_BYTES=...] marker.

MCP Connector Setup (Claude Desktop / Claude Code)

Append to your cli