Registering an MCP server¶

A server is either a local command that mcprack runs per user (stdio), or a network endpoint it relays to (http or sse).

With the command line¶

# a local stdio server
sudo mcprack server create zabbix \
    --label "Zabbix" --transport stdio \
    --command /usr/bin/zabbix-mcp \
    --set-env ZABBIX_URL=https://zabbix.example.com/api_jsonrpc.php \
    --enabled
sudo mcprack secret set zabbix ZABBIX_TOKEN

# a network server
sudo mcprack server create netbox \
    --label "NetBox" --transport http \
    --url https://netbox.example.com/mcp --enabled

server create is idempotent: running it again updates the server. Test it:

sudo mcprack server test zabbix --timeout 30

The command performs the MCP handshake and prints the tools, resources and prompts. Test a command without registering it (the form used by package autopkgtests):

sudo mcprack server probe /usr/bin/mcp-server-filesystem --set-env FS_READONLY=true

In the web interface¶

Admin → Servers → New walks through the same fields. Autodetect proposes environment variables from the server’s manifest or documentation; suggestions are never saved until you submit the form. Creating or editing a server asks you to confirm your password again if you have not signed in recently (Fresh authentication for dangerous actions).

Rules for commands and URLs¶

Both are checked when the server is saved and again when it is used (Policies for commands, URLs and installs):

A command in /tmp, /var/tmp, /dev/shm … or a relative path is refused. ALLOWED_COMMAND_DIRS makes this an allowlist.
A URL must be http or https, without credentials, and must not point at a link-local or cloud metadata address.
command wins over url when both are set; leave the unused one empty.

Installing packages for a server¶

Admin → Install installs a pip or npm package or pulls a Docker image and registers it. Inputs are validated, packages must be pinned to an exact version (INSTALL_REQUIRE_PINNED), pip installs wheels only (INSTALL_ALLOW_SOURCE_BUILDS changes that) and npm never runs lifecycle scripts. If you use ALLOWED_COMMAND_DIRS include /var/lib/mcprack/installs.

Servers that register themselves¶

A server shipped as a Debian package with a companion package appears in the catalog as soon as the companion is installed — see MCP servers with a mcprack companion.

Enabling and disabling¶

sudo mcprack server disable zabbix     # hides it from everybody
sudo mcprack server enable zabbix
sudo mcprack server show zabbix
sudo mcprack server list