# simscout

simscout is a small local bridge to esimoa's hosted MCP
server, which catalogues travel eSIM plans: pick a
destination, say how long the trip is and how much data
you need, and the catalog answers with matching plans,
their prices in KRW, and a link to each plan's page on
esimoa.com where a purchase would happen.

The bridge keeps no catalog of its own. It serves the
upstream server's tool list locally, exactly as captured
from the live endpoint, and forwards each tool call
upstream, returning the result untouched. The whole
captured surface only reads — searching, fetching one
plan, comparing a shortlist and listing destinations —
and there is no checkout or payment tool in it.

## Tools

- `search_esims` — search the catalog for a destination.
  All filters are optional: `country` (ISO code or name
  in any language, e.g. `JP` or `Japan`), `days` (trip
  length), `data_gb` / `max_data_gb`, `unlimited`,
  `countries` (multi-country trips, up to 8), `data_type`
  (`daily` or `total`), `local_number`, `network`
  (`local` or `roaming`), `multi_country`, `min_price_krw`
  / `max_price_krw`, `provider`, `hotspot`, `five_g`,
  `sort` (`recommended`, `price`, `data`, `price_per_gb`
  or `validity`), `limit` (1-10, default 5) and `lang`.
  Each result carries an `id` and a plan page `url`.
- `get_esim` — the full details of one plan. Required:
  `id` (from `search_esims`). Optional: `lang`.
- `compare_esims` — two to five plans side by side:
  price, data, validity, price per GB, coverage, network,
  hotspot and local phone number, plus which plan wins
  each of lowest price, most data, longest validity and
  lowest price per GB. Required: `ids`. Optional: `lang`.
- `list_countries` — every destination where plans are
  sold, with the plan count and the lowest price per
  country. Optional: `query` (name or ISO filter) and
  `lang`.
- `search` — free-text search in the search/fetch format
  used by ChatGPT deep research, e.g. "Japan 7 days
  unlimited". Required: `query`. Returns ids for `fetch`.
  When you can fill filters, prefer `search_esims`.
- `fetch` — one plan as a document, by an id returned
  from `search`. Required: `id`. For plans found with
  `search_esims`, use `get_esim` instead.

## Configuration

- `ESIMOA_MCP_URL` (optional) — override the upstream
  endpoint. Defaults to `https://api.esimoa.com/mcp`.
  (The override hook is this rebuild's own labelled
  reconstruction.)
- `ESIMOA_API_KEY` (optional) — when set, every
  upstream request carries an `X-API-Key: <key>` header
  (a partner key adds the partner's affiliate code to
  buy links). When it is not set, no key header is sent
  and the upstream returns plain links. No
  `Authorization` header is ever sent. (This forwarding
  is also a labelled reconstruction; the original
  surface was captured keyless.)

### Forwarding mechanics

On the first tool call the client opens a streamable
HTTP session with the upstream: a JSON-RPC `initialize`
request (protocolVersion `2025-03-26`, clientInfo name
`simscout`), then a `notifications/initialized`
notification, then the `tools/call` request carrying
the caller's arguments unchanged. When the upstream
answers `initialize` with an `Mcp-Session-Id` header,
that value rides on every later request of the session,
which is reused for the life of the process. Replies
may arrive as plain JSON or as server-sent events;
both are read.

Successful upstream results pass through verbatim,
including any `isError` flag the upstream sets.
Failures — a JSON-RPC error, a non-2xx status, an
unreadable response, or a request that cannot be
completed — come back as an `isError` result whose
text starts with `simscout error:` (this rendering
is this rebuild's own labelled reconstruction).

## CLI

Each tool is also a subcommand taking one JSON argument
string (omit it for tools that take none):

```bash
npx @reneturcios/simscout search_esims '{"country":"JP","days":7,"sort":"price"}'
npx @reneturcios/simscout get_esim '{"id":"plan-9"}'
npx @reneturcios/simscout compare_esims '{"ids":["plan-9","plan-11"]}'
npx @reneturcios/simscout list_countries '{"query":"Japan"}'
npx @reneturcios/simscout --version
```

Exit codes: `0` on success, `1` on an `isError`
result, `2` on a usage error.

## MCP server

```bash
npx -y @reneturcios/simscout mcp
```

MCP client config:

```json
{
  "mcpServers": {
    "simscout": {
      "command": "npx",
      "args": ["-y", "@reneturcios/simscout", "mcp"]
    }
  }
}
```

## Docker

```bash
docker run -i ghcr.io/cloudcorprecords/simscout
docker run --rm ghcr.io/cloudcorprecords/simscout --version
```

The container's default command is `mcp`, so the first
form is a stdio MCP server; any other arguments reach
the CLI normally.

## Development

```bash
npm install
npm run build
npm test
npm run dev
```

The test suite runs entirely against a stubbed
JSON-RPC upstream — no live network calls.

## License

MIT — see `LICENSE`.