train-mcp

MCP server for Austrian train planning where the agent writes JavaScript instead of only filling fixed JSON forms.

The server exposes a constrained codemode API inside an isolated QuickJS sandbox. The agent can write small scripts that search stations, inspect intermediate results, chain journey calls, filter alternatives, and return a shaped answer. The sandbox has no general network or filesystem access; it can only call the train-planning functions exposed by the MCP server.

Architecture

flowchart LR
  agent["MCP client / agent"]
  search["search tool"]
  execute["execute tool"]
  sandbox["QuickJS sandbox"]
  catalog["Catalog helpers"]
  transit["Train functions"]
  oebb["OEBB transport API"]

  agent --> search
  agent --> execute
  search --> sandbox
  execute --> sandbox
  sandbox --> catalog
  sandbox --> transit
  transit --> oebb

Loading

MCP tools

train-mcp exposes exactly two MCP tools:

• search: catalog-only JavaScript execution. Use it to discover available train functions and their input schemas.
• execute: train-planning JavaScript execution. Use it to call OEBB-backed train functions.

Both tools accept one input field:

{
  "code": "return await codemode.listTools({});"
}

search

search only exposes catalog helpers:

• codemode.getCatalog({})
• codemode.listTools({})

Example:

const tools = await codemode.listTools({});
return tools;

execute

execute exposes the actual train functions:

• codemode.oebbPlanJourney(...)
• codemode.oebbPlanTour(...)
• codemode.oebbResolveItineraryStops(...)
• codemode.oebbLocations(...)
• codemode.oebbDepartures(...)
• codemode.oebbJourneys(...)
• codemode.oebbTrip(...)

Call functions directly on codemode. Do not use codemode.callTool(...).

Example:

const journey = await codemode.oebbPlanJourney({
  from: "Wien Hbf",
  to: "Linz Hbf",
  departure: "2026-05-11T09:00:00+02:00",
  results: 1,
  responseMode: "summary"
});

return journey;

Because this is JavaScript, the agent can do multi-step work in one tool call:

const from = await codemode.oebbLocations({ query: "Wien Hbf", results: 3 });
const to = await codemode.oebbLocations({ query: "Linz Hbf", results: 3 });

const journey = await codemode.oebbPlanJourney({
  from: from[0].id,
  to: to[0].id,
  departure: "2026-05-11T09:00:00+02:00",
  results: 3,
  selection: "fastest",
  responseMode: "summary"
});

return {
  resolved: { from: from[0], to: to[0] },
  journey
};

Connect

Codex CLI:

codex mcp add train-mcp --url https://train.floritzmaier.xyz/mcp

Claude Code:

claude mcp add --transport http train-mcp https://train.floritzmaier.xyz/mcp

Local development:

cd mcp
cargo run