Environment variables

Three variables, all read once at startup. There is no config file.

HETZNER_API_TOKEN

Required. Hetzner Cloud API token for the project that holds the zones.

Create it in the Cloud Console under your project → Security → API tokens. Choose Read & Write for the full tool set, Read for the query tools only.

• Sent as Authorization: Bearer … on every request.
• Deleted from process.env once read.
• Never logged, never included in an error message or a tool result.

Without it the server still starts, completes the MCP handshake and lists all tools — registries and sandbox inspectors need that — but every call fails with setup instructions and nothing reaches the API.

DANGER

A token from the old DNS Console (dns.hetzner.com) does not work. That API was shut down in May 2026.

HETZNER_READ_ONLY

Optional, default false. Accepts true, 1 or yes, case-insensitively.

When set, only these seven tools are registered:

list_zones · get_zone · export_zonefile · list_rrsets · get_rrset · list_zone_actions · get_zone_action

The write tools are not registered at all, so a client asking for delete_zone gets a protocol-level "tool not found". This is not a call-time refusal — there is no code path from a write request to the API.

HETZNER_API_BASE_URL

Optional, default https://api.hetzner.cloud/v1. Trailing slashes are stripped.

Intended for pointing at a local mock during development. Validated before anything is sent, because the token goes to whatever this names:

Rule	On violation
Must parse as a URL	exit
Must be https (http only for loopback hosts)	exit
Must not contain credentials (https://user:pass@…)	exit
Non-default host	warning

Loopback hosts are localhost, 127.0.0.1 and [::1].

The value is never printed back on a parse failure — a malformed URL can still contain a user:token@ part, and startup messages end up in client logs.

Also deleted from process.env once read.

Not configurable

For completeness, the constants you might otherwise look for:

Behaviour	Value
Request timeout	30 s
Redirect handling	refused
Confirmation token TTL	5 minutes, single use
Pending confirmation tokens	100 max, oldest evicted
Per-value truncation	4 000 characters
Per-result truncation	200 000 characters
Error body truncation	2 000 characters; HTML dropped
Redacted key pattern	tsig_key, token, secret, password, credential