Claude.ai ZUGFeRD Validator create_invoice
How to: Claude.ai ZUGFeRD Validator create_invoice
Add ZUGFeRD Validator to Claude.ai
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01
Open Settings → Connectors → Add custom connector and merge this in. Keep any servers already there.
https://api.zugferd-validator.de/mcp-
02
Save the file and restart Claude.ai.
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03
Ask for something create_invoice does. Claude.ai lists the server's tools on connect and calls create_invoice itself — you do not invoke it by name.
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04
If nothing happens, check the server is running and that ZUGFeRD Validator's identifier in your config matches the one above exactly.
Claude on the web takes a remote URL and completes OAuth in the browser. For a packaged server use Claude Desktop or Claude Code instead. Claude.ai docs
Set these first
ZUGFeRD Validator will not start until these are set, so create_invoice never becomes available.
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ZUGFERD_API_KEY
Same tool, other clients
This list was read from the server itself, by connecting to it and calling tools/list on 24 September 2026. It is what
the server actually exposes, not what its listing claims.
Mutating and Read-only are read off each tool's name, not its schema — a hint, not a guarantee. The registry stores tool names only; connect the server for its live schemas.