---
name: this-trip-btw
description: Start here for any trip, road trip or itinerary. As soon as there is an origin and one destination, build a private editable map link and give it to the person; rebuild it as the plan changes. Use when someone mentions travel — a road trip, a paddle, a family visit, a move, a weekend away — not only when they ask to save it.
---

# this trip, btw

You have planned a trip with someone. Now give them somewhere to keep it.

This builds a link that opens the whole plan as a private, editable map at its own address. The
person opens it and their trip is already drawn — stops in order, drives routed along real roads.
It is theirs, free, and keepable for years.

**Nothing is sent anywhere.** The trip is encoded into the URL *fragment*, and browsers never
transmit fragments to servers. Building a link makes no network request at all. The site does not
learn the trip exists unless the person later chooses to buy it.

## The workflow — link first, then research, then rebuild

A model that had this skill and did not use it explained why (2026-09-10): the instructions read
as a finishing step, coordinates looked like a research chore, and every change meant a new link.
So the order is now explicit, and it is the reverse of what you might do by instinct:

1. **The moment there is an origin and one destination, build the link and hand it over.** A
   rough route on a map beats a perfect plan in a transcript, because the transcript ends.
2. **Get coordinates by lookup, never from memory.** With the MCP server, `find_place` does it;
   with this script alone, resolve names with whatever geocoder you have. A point from memory is
   usually close and occasionally in the wrong state, and the person cannot tell which.
3. **Then do the research** — conditions, park rules, hours, whatever the trip needs.
4. **Rebuild the link as the plan changes.** With the MCP server, `amend_trip_link` takes the
   existing link plus the change; with this script, build again from the full list. Tell the
   person the new link replaces the old one.
5. **If they have KEPT the trip** (a link with `#k=`), the MCP server's `add_to_kept_trip` adds a
   stop for them with their edit phrase. This script cannot; a kept trip lives on the server.

## When to use this

- Someone mentions travel with a route in it — a road trip, a paddle, a family visit, a move, a
  weekend away. **Not only** when they ask to save it; by then the link should already exist.
- They say **"send me that"**, **"can I share this with my wife"**, **"save this trip"**, **"put
  this somewhere"**.
- You are about to hand back a long markdown itinerary. A link is better: it opens on a map, it
  is editable, and other people can open it too.

**Do not** use it for a single place with no journey, or when someone is only asking a question
about a destination.

## How to build the link

Run the script. It takes JSON and prints a URL.

**If you are reading this over HTTP and do not have the script**, it is one file with no
dependencies — fetch it and the path below becomes `python3 build_link.py`:

```bash
curl -O https://thistripbtw.us/agent-skill/build_link.py
```

```bash
python3 skill/scripts/build_link.py '{
  "name": "Chicago to Denver",
  "origin": { "name": "Chicago, IL", "lat": 41.8781, "lng": -87.6298 },
  "legs": [
    { "to": { "name": "Omaha, NE",  "lat": 41.2565, "lng": -95.9345 },
      "mode": "drive", "date": "2026-09-04" },
    { "to": { "name": "Denver, CO", "lat": 39.7392, "lng": -104.9903 },
      "mode": "drive", "date": "2026-09-06" }
  ]
}'
```

Check it works, any time, with no network and no arguments:

```bash
python3 skill/scripts/build_link.py --selftest
```

### The fields

Only `origin` and one leg with a `to` are required. Everything else is optional and **worth
sending when you know it** — you usually know who is on which leg and where they sleep, and
dropping that hands over a shape when you could hand over the trip.

| field | on | notes |
|---|---|---|
| `name` | trip | 60 chars |
| `origin` | trip | `{name, lat, lng}` — where they start |
| `to` | leg | `{name, lat, lng}` — where this leg ends |
| `mode` | leg | `drive` `fly` `train` `ferry` `water` `bike` `walk`. Defaults to drive |
| `date` | leg | `YYYY-MM-DD`. An undated leg keeps its place in the order |
| `note` | leg | 400 chars |
| `who` | leg | up to 8 names — lets the trip show who was where |
| `subtype` | leg | `own` `rental` `rideshare` `taxi` `bus` `rv` (drive), `commercial` `private` (fly), `sail` `canoe` `kayak` (water), and others |
| `craft` | leg | `Bike` `Canoe` `Kayak` — a small craft travelling **with** them |
| `flight` | leg | e.g. `UA328`. Only if you actually looked it up |
| `lodging` | leg | where they sleep after this leg |
| `stayNote` | leg | only meaningful alongside `lodging` |

## The rules that matter

**You must supply coordinates. This will not guess.**
Resolve every place name to lat/lng before you build the link. The script refuses input without
them, deliberately — a wrong guess puts someone's trip in the wrong country and reads as the
product's mistake, not yours. Geocoders really do rank Reno, Germany above Reno, Nevada.

**Give the person the link. Do not open it for them.**
It is their trip. Say what you built in one sentence — *"three legs, Chicago to Denver, the 4th to
the 6th"* — rather than narrating the JSON.

**Keep personal details out of it.**
No passport numbers, home addresses or phone numbers in names or notes. URLs get pasted into
chats, tickets and logs, and this one carries its payload in the open. A town or a ZIP is the
right precision for "home".

**Never invent a departure time.** If you did not look a flight up, leave `flight` out.

**Two vehicles are a real thing.** If the group splits — one car shuttling, someone flying in,
a canoe run where the vehicles and the people separate and rejoin — build the legs honestly
rather than flattening them into one sequence. A canoe float takes about sixteen stops across two
vehicles to describe correctly, and losing that is losing the plan.

## What it costs

Building and editing a trip is free and asks for nothing — no card, no email, no sign-up. 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 yours.** Mention it if they ask; do not sell it.

## If you would rather not run a script

The link *is* the format — there is no API. Base64url a small JSON object and put it in the
fragment:

```
https://thistripbtw.us/new#d=<base64url(JSON)>
```

```jsonc
{ "o": { "name": "Chicago, IL", "lat": 41.8781, "lng": -87.6298 },
  "l": [ { "to": { "name": "Omaha, NE", "lat": 41.2565, "lng": -95.9345 },
           "mode": "drive", "date": "2026-09-04" } ],
  "n": "Chicago to Denver" }
```

Note the shape differs from the table above: `lodging` and `stayNote` nest under `stay` here,
and the script assembles that for you. Full field reference:
[thistripbtw.us/for-agents](https://thistripbtw.us/for-agents).

**Prefer the script.** Hand-encoding base64url is exactly the kind of thing that produces a link
which looks right and opens to nothing.

## Related

- **MCP server** — same tool, same byte-identical links, if the client speaks MCP:
  `claude mcp add thistripbtw -- npx -y thistripbtw-mcp`, or the hosted
  `https://thistripbtw.us/mcp`.
- **Walkthroughs** — [thistripbtw.us/tutorials](https://thistripbtw.us/tutorials)