ZUGFeRD Validator

ZUGFeRD Validator is a remote MCP server: there is nothing to install. Its endpoint is https://api.zugferd-validator.de/mcp, served over Streamable HTTP. In an assistant that accepts remote MCP servers (often under a setting named connectors, integrations or tools), add a new server and give it this URL; in a client configured by file, add it as a remote (HTTP) server with the same URL.

The registry entry declares an HTTP header for the connection: X-Api-Key (required, secret). A secret header usually carries an API key or token issued by the service; clients that accept custom headers set it with the server's URL.

It can also run locally from a Node.js package published to the npm registry: zugferd-mcp-client version 1.1.1. It speaks MCP over stdio, so the client starts it as a program and talks to it through standard input and output. It needs Node.js; clients usually start it with npx — the usual command is npx -y zugferd-mcp-client@1.1.1. It reads the environment variable ZUGFERD_API_KEY (required, secret); set it in the client's configuration for this server.

In the mcpServers JSON format that many desktop and editor MCP clients read, the entry looks like this (placeholders in angle brackets):

{
  "mcpServers": {
    "validator": {
      "command": "npx",
      "args": [
        "-y",
        "zugferd-mcp-client@1.1.1"
      ],
      "env": {
        "ZUGFERD_API_KEY": "<secret>"
      }
    }
  }
}

Derived from the registry entry, not tested here. What the server does, and on what terms, is set by its publisher; check its repository or website before giving it access to your accounts or files. How to add an MCP server to an assistant · Before you connect