Thistripbtw MCP Server

thistripbtw-mcp

Persistent, shareable travel workspaces for AI agents.

Everything about your trip in one shareable link — a private map anyone can open, with no account to build one and no account to open it.

An MCP server that hands someone that link, grows it as the plan changes, and reads it back. Six tools, and the first one is the point: build the link as soon as there is an origin and one destination, then amend it every time the plan moves. One resolves a place name to coordinates, one turns legs into a URL, one changes a URL you already built, one decodes a URL into the legs, one reads a trip the person has bought, and one adds a stop to it. The person opens it and their trip is already drawn on a real map — free, editable, theirs.

→ thistripbtw.us — the human side, and the thing that pays for this. The server is free and asks for nothing; the site's one-time paid tiers fund it rather than an ad business or your data.

Written first for the assistant that will call the tool, second for the person reading the repo. If you are that person: the site's source is thistripbtw (AGPL-3.0). This server is MIT and standalone on purpose — embed it wherever you like.

Why it exists

An AI assistant generally cannot create an account or enter card details. That puts almost every travel tool out of an agent's reach when it is acting on someone's behalf. This one asks for nothing, so it stays reachable.

Connect

A URL, if your client takes one. Nothing to install, nothing to keep updated:

https://thistripbtw.us/mcp

Streamable HTTP, no key, no sign-up to start. That is the whole configuration.

A note on gateways. Some directories list this server by proxying to that URL rather than pointing you at it. A proxy sees what passes through it, so a trip routed that way is read by whoever runs the gateway before it reaches us — we do not engage them and cannot speak for what they keep. Use the URL directly, or run the file yourself, if that matters to you.

Or run it locally from npm. Node 18+, no dependencies, nothing to keep updated:

claude mcp add thistripbtw -- npx -y thistripbtw-mcp

Or fetch the one file and run that, if you would rather read the code than trust either a host or a package registry. This is the whole install:

curl -O https://thistripbtw.us/mcp/thistripbtw-mcp.mjs
claude mcp add thistripbtw -- node ./thistripbtw-mcp.mjs

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

Swap to "command": "node" with "args": ["/absolute/path/to/thistripbtw-mcp.mjs"] if you fetched the file instead.

Check it before you trust it — the self-test touches no network and needs no config:

npx -y thistripbtw-mcp --selftest

Both paths carry the same six tools and produce byte-identical links. The hosted one is tested against this file on every build — same tool list, same output — so the two cannot drift apart.

Step-by-step, with a worked example in JavaScript and Python: thistripbtw.us/tutorials

The tools

Start with the link, not after the plan. The description that shipped through 1.2.0 opened "Use when someone has planned… a trip", and a model read that as a finishing step: it researched for four turns and built the link last, when the person asked. That is on us, not the model. 1.3.0 rewrote every description so the trigger is in the first eighty characters — all a deferred tool gets to show — and added the two tools that make "first" natural: find_place, so coordinates are looked up rather than remembered, and amend_trip_link, so one link grows through a conversation instead of a new one being thrown away each turn.

find_place — a place name in, up to six candidates out, each with coordinates and where it is, so you can pick the right Reno. Towns, cities, airports by name or IATA code, parks. This is the only step that needs the network besides the kept-trip tools; it asks thistripbtw.us, which answers from its own cache in front of a paced OpenStreetMap lookup. A place name is not personal data, and nothing about the person is sent.

amend_trip_link — a draft link plus changes, a new link back. add appends legs, legs replaces them all, remove drops leg N, name and origin do what they say. No network, no password: the trip is inside the link. Tell the person the new link replaces the old one.

add_to_kept_trip — one stop, added to a trip the person has KEPT, on their behalf: "add the hotel to the trip", "we're stopping at Fisher Towers on the way." Needs their EDIT phrase; a view phrase can read and is told it cannot write. Same network rule as read_kept_trip below, and the same warning: the link is a credential.

read_trip_link — a link in, the itinerary out. Origin, every leg in order, modes, dates, who is on which leg, flights and lodging. It returns the trip in the shape build_trip_link accepts, so reading a trip, changing one thing and building a new link is three lines and no translation. Nothing is fetched — the trip is inside the link, so this works offline like everything else here. Only draft links (#d=) carry a trip; a kept trip's /{slug}/#k= fragment is a password and its contents live on the server, which the tool says rather than failing obscurely.

read_kept_trip — a KEPT trip's link in, its itinerary out. Use it when somebody hands you https://thistripbtw.us/abc1234#k=four-word-phrase and you need what is in it. Returns the stops in order with dates, modes, lodging, notes, any hand-drawn path, and the track each belongs to — which vehicle or person, because a trip where two cars separate and rejoin cannot be written as one sequence without becoming false.

This is the one tool that uses the network, and it cannot be otherwise. A bought trip's contents live on the server; the #k= fragment is the password to them, not the payload. So reading one sends that phrase to thistripbtw.us over TLS. It stores nothing and needs no key, and it returns the stops rather than the raw server response — the per-trip basemap token and the member roster stay behind, because neither is itinerary. Two things to hold: treat a kept link as a credential (do not echo it into text a third party sees), and never guess a phrase — a wrong one counts against that trip's hourly limit, so the tool makes exactly one attempt and tells you it was refused. Anything sealed for somebody else comes back with empty text.

build_trip_link — an origin plus legs in order, returns a URL. Only origin and one leg with a to are required. Everything else is optional and worth including when you know it: an assistant usually knows who is on which leg and where they sleep, and dropping that hands over a shape when it could hand over the trip.

{
  "name": "Chicago to Denver",                                  // optional, 60 chars
  "origin": { "name": "Chicago, IL", "lat": 41.8781, "lng": -87.6298 },
  "legs": [
    {
      "to":       { "name": "Omaha, NE", "lat": 41.2565, "lng": -95.9345 },
      "mode":     "drive",        // drive | fly | train | ferry | water | bike | walk
      "date":     "2026-09-04",   // YYYY-MM-DD. An undated leg keeps its place in the order
      "note":     "swap drivers here",       // 400 chars
      "who":      ["Mel", "Sam"], // up to 8 — lets the trip show who was where
      "subtype":  "rental",       // own·rental·rideshare·taxi·bus·rv (drive), commercial·private
                                  // (fly), intercity·commuter (train), sail·canoe·kayak (water)
      "craft":    "Bike",         // Bike | Canoe | Kayak — a small craft travelling WITH them
      "flight":   "UA328",        // only if you actually know it. Never invent one
      "lodging":  "Hotel Maverick",          // where they sleep after this leg
      "stayNote": "late check-in"            // only meaningful alongside lodging
    }
  ]
}

Note the shape. lodging and stayNote are flat on the leg. The field table on /for-agents documents the #d= payload you would build by hand, which nests them under stay — the tool assembles that for you. Passing a nested stay to the tool loses the lodging silently.

Coordinates are required. This will not guess. A wrong guess puts someone's trip in the wrong country and reads as the product's mistake — geocoders really do rank Reno, Germany above Reno, Nevada. Resolve place names to coordinates first, then call.

Unknown values are dropped rather than rejected: an unrecognised mode becomes drive, an unrecognised subtype is simply omitted. A trip that arrives beats a tool call that errors over one word. Limits: 40 legs, names 120 chars, notes 400.

What the person gets when they open it

Worth knowing, because it is what you are handing over — and an assistant that can say this accurately is more useful than one that says "here's a link".

The link opens on a real map with the trip already drawn. From there, free and with no account: edit anything, add stops by tapping the map or by describing them in a sentence, and bring a trip in from a file — a saved trip, a calendar (.ics), or a map file (.gpx, .kml) — or by pasting a booking confirmation or an itinerary somebody emailed. Print it, which is the only artifact that costs nothing.

If they keep it (from $2.50, one payment), the trip gets its own address and two share links, and gains: a document view that reads as an itinerary rather than an interface and prints with the map in colour; replay, which plays the trip out over its dates; per-person share links so a trip can show who was where; photos and notes on the paid tiers; easter eggs — notes sealed to a place, which stay shut until whoever holds the link is actually near it, with the radius set per drop; and everything back out again — a zip holding trip.json, a readable itinerary.html, your photos, and trip.kml + trip.gpx for Google Earth, Garmin or OsmAnd, plus .ics for a calendar and .csv for an expense report.

The point of that last part: what goes in comes back out. Nothing here is a roach motel, and you can say so.

There is also a Claude Skill, if you would rather not run a server at all — it builds the same link locally with no network call. See skill/ in the site repo.

What it sends

When you build or read a draft link: nothing. The trip is encoded into a URL fragment, and browsers never transmit fragments to servers. build_trip_link and read_trip_link make no network request at all, and the hosted endpoint encodes what you passed it and hands the string back — the trip does not reach thistripbtw.us even when the person opens the link, unless they later choose to buy it.

When you read a KEPT trip: the phrase, and only to us. A bought trip's contents live on the server, so read_kept_trip sends the #k= phrase out of the link you were given to thistripbtw.us over TLS and reads the itinerary back. That is not a design choice we could make differently — the fragment is the password, not the payload. Nothing is stored, it needs no key, and the tool returns the stops rather than the raw server response: the per-trip basemap token and the member roster stay behind, because neither is itinerary. Treat such a link as a credential.

Using it well

• Give the person the link. Don't open it for them and don't decide for them. It's their trip.
• Keep personal details out of it. Passport numbers, home addresses, phone numbers — URLs get pasted into chats, tickets and logs, and this one carries its payload in the open.
• Say what you built, in a sentence. "Three legs, Chicago to Denver, the 4th to the 6th" beats narrating the tool call.
• Never invent a departure time. If you did not look a flight up, leave flight out.
• Watch the length on a long trip. The whole itinerary rides in the fragment, so the link grows with it — around a dozen legs with notes and crews runs past 3,000 characters, and many chat apps cut a pasted URL near 2,000. Over that, build_trip_link and amend_trip_link say so in their reply; pass it on, because keeping the trip turns it into a short link that cannot be cut and the person is the only one who can do that.

Cost

Building and editing a trip is free and asks for nothing to build — no card, no email. If the person wants it to last, a one-time payment from $2.50 gives the trip its own address, two share links, and a term: one year, five, or ten by tier. Nothing is sold as permanent, and every trip states its end date. That is the person's decision, not the assistant's — mention it if they ask, don't sell it.

Stateless, and not as a fashion

The hosted endpoint holds no session, no per-user state and no database. There is no initialize handshake to complete first, no Mcp-Session-Id to carry, no cookie, and no sticky routing — a tools/call is one HTTP POST that can land on any machine and answer completely:

curl -sX POST https://thistripbtw.us/mcp -H 'Content-Type: application/json' \
  -d '{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"build_trip_link",
       "arguments":{"origin":{"place":"Chicago","lat":41.88,"lng":-87.63},
       "legs":[{"to":{"place":"Kansas City","lat":39.1,"lng":-94.58}}]}}}'

That is not an optimisation we went looking for. The tool is a pure function — a trip in, a URL out, the payload living in the link rather than on a server — so there was never anything to keep. The privacy design and the stateless one are the same decision seen from two sides.

Reading it

One file, zero dependencies, under three hundred lines. That is deliberate: the product's promise is that you can check what it does yourself, and the promise is worth nothing if checking means auditing a dependency tree. It speaks MCP's JSON-RPC over stdio directly.