MCP server
Use invowerk in your AI assistant
Claude, ChatGPT, Cursor, and other AI assistants can call invowerk directly over the Model Context Protocol (MCP). The server runs online, so there is nothing to install.
https://api.invowerk.dev/mcp/Streamable HTTP · 6 tools · works without an API key
Tools
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Check an e-invoice
Check an e-invoice against EN 16931 and German rules.
validate_invoice1 credit -
Render an e-invoice as HTML
Render an XML e-invoice (UBL or CII, e.g. XRechnung) as a readable HTML page.
render_invoice1 credit -
Explain error codes
Explain rule codes in plain language. Works without an API key.
explain_errorsFree -
Create an e-invoice from JSON
Create a valid EN 16931 e-invoice (UBL or CII XML) from JSON.
generate_invoice5 credits -
Read an e-invoice into JSON
Read an existing e-invoice into JSON keyed on EN 16931 Business Terms.
parse_invoice2 credits -
Convert an e-invoice between UBL and CII
Convert an e-invoice to UBL or CII. The result is checked before it is returned.
convert_invoice3 credits
Connect
- In Claude (web or desktop app), open Customize → Connectors.
- Click + and choose Add custom connector.
- Enter a name and this URL, then click Add:
https://api.invowerk.dev/mcp/Works on every Claude plan; the free plan allows one custom connector. Claude connects without an API key. When a tool needs your account, Claude asks you to sign in (free, no card). Claude's guide
- Turn on Developer mode in ChatGPT's settings.
- Create an app for a remote MCP server with this URL and no authentication:
https://api.invowerk.dev/mcp/Developer mode is available on the web for Plus, Pro, Business, Enterprise, and Education plans. ChatGPT connects without an API key. When a tool needs your account, ChatGPT asks you to sign in (free, no card). OpenAI's guide
Run this in your terminal:
claude mcp add --transport http invowerk https://api.invowerk.dev/mcp/With an API key:
claude mcp add --transport http invowerk https://api.invowerk.dev/mcp/ --header "X-API-Key: YOUR_API_KEY"With an API key, add the server to ~/.cursor/mcp.json instead:
{ "mcpServers": { "invowerk": { "url": "https://api.invowerk.dev/mcp/", "headers": { "X-API-Key": "YOUR_API_KEY" } } }}With an API key, add the server to .vscode/mcp.json instead:
{ "servers": { "invowerk": { "type": "http", "url": "https://api.invowerk.dev/mcp/", "headers": { "X-API-Key": "YOUR_API_KEY" } } }}Run this in your terminal:
codex mcp add invowerk --url https://api.invowerk.dev/mcp/With an API key, add this to ~/.codex/config.toml instead:
[mcp_servers.invowerk]url = "https://api.invowerk.dev/mcp/"http_headers = { "X-API-Key" = "YOUR_API_KEY" }Any client that supports remote MCP servers connects with the URL above over Streamable HTTP. Most read a JSON block like this one:
{ "mcpServers": { "invowerk": { "url": "https://api.invowerk.dev/mcp/" } }}Some clients name the field serverUrl or httpUrl instead of url, or need "type": "streamableHttp". Your client's MCP documentation has the exact form. An API key goes in the X-API-Key header.
Free to use, more with an API key
- Without an API key the server works right away, with 10 free credits a day per IP address.
- With an API key the limits are higher, and each call uses the credits shown next to the tool.
- Claude and ChatGPT cannot send an API key. Instead they ask you to sign in, and then use your account.