viafrei

A stdio↔Streamable-HTTP bridge for the ViaFrei MCP server — German road, parking, charging, rail and fuel data, answered by your AI assistant.

npx viafrei

What this is

ViaFrei is a Germany-wide transport intelligence layer whose interface is the assistant rather than an app: open data → PostgreSQL/PostGIS → MCP tools over Streamable HTTP at https://mcp.viafrei.de/mcp.

Most MCP clients speak Streamable HTTP and should connect to that URL directly — they do not need this package. Some clients still speak only stdio. This bridge is for those: it runs locally, exposes a stdio MCP server, and relays every request to the public endpoint.

So the bridge is a transport shim. It holds no data, no database and no credentials, and it makes no decision about an answer.

Related MCP server: germany-mcp-server

Using it

Node 22 or newer. There is nothing to install: npx fetches it when the client starts it.

Claude Desktop (claude_desktop_config.json) — and the same three lines fit any client that takes an stdio MCP server, including the .mcp.json an IDE reads:

{
  "mcpServers": {
    "viafrei": {
      "command": "npx",
      "args": ["-y", "viafrei"]
    }
  }
}

A different endpoint — your own deployment, or a server running locally on port 3000:

{
  "mcpServers": {
    "viafrei": {
      "command": "npx",
      "args": ["-y", "viafrei", "--url", "http://127.0.0.1:3000/mcp"]
    }
  }
}

VIAFREI_MCP_URL does the same thing for clients that pass environment variables rather than arguments. A flag wins over the variable; the variable wins over the built-in default.

Options

Environment: VIAFREI_MCP_URL, VIAFREI_MCP_TIMEOUT_MS.

When something is wrong

The bridge prints one line to stderr and exits with a code that says what happened. No stack traces:

viafrei: cannot reach https://mcp.viafrei.de/mcp: connection refused (ECONNREFUSED) - check the URL, or pass --url for a different endpoint

An established session is allowed to wobble — a dropped event stream is a warning, not an exit, and the bridge reconnects. It is not allowed to be dead in silence: several failures in a row with nothing succeeding in between end the process with the code above, so the client that started it finds out.

What it does not do

No telemetry, no analytics, no usage counter, no update check. It writes no file outside the OS temp directory, and it stores no credential — --header is passed through to the endpoint and never persisted or logged.

It also does not follow a redirect off the origin you pointed it at. Your headers go to that origin and nowhere else: a cross-origin redirect is refused with one line naming both ends, so a server cannot forward your API key somewhere you did not choose. Same-origin redirects are followed normally.

What the server can answer

The tool catalogue is not duplicated here, deliberately. A pasted list goes out of date the first time a description changes on the server, and then this page describes a server that no longer exists. There is one source of truth and it is the running server:

• point any MCP client at https://mcp.viafrei.de/mcp and call tools/list;

• or read https://viafrei.de for the catalogue rendered from that same list.

Using the data you get back

Every result carries an attribution line. Show it to the person reading the answer. The full register lives at the resource viafrei://attribution.

Two constraints matter more than the rest, because getting them wrong is a licence breach rather than a style problem:

• MTS-K fuel prices are consumer information only. No redistribution in any form — that includes aggregates, comparisons, price tables and anything derived. Answer the person who asked; do not build a product out of it.

• DELFI public-transport data is CC BY-SA 4.0. Share-alike travels with anything derived from it, and it must not be blended into a result under a different licence.

See NOTICE and LICENSE.

The server itself

The MCP server is offered as a hosted service, and its source is closed. The schema, the ingest workers, the provider connectors and the query layer are not in this repository and are not published. What is public is the part that is meant to be: the tool names, their descriptions, their input schemas, the shape of the results and the attribution lines — everything a client reads from tools/list, which is the product surface.

This is said plainly so nobody spends an evening looking for the server code.

Contributing

Yes, please — see CONTRIBUTING.md. Issues and discussions are open. The bridge is small and self-contained, which is exactly what makes it a reasonable thing to send a first patch to.

Security

Never open a public issue for a key, a token or anything that looks like one. See SECURITY.md for the private reporting path.

Licence

Apache-2.0 for this code. Data obtained through the server keeps its provider's licence — see NOTICE.