# previewglow

previewglow is a small local bridge to the hosted
Shareglow MCP server, which looks after link previews
and Open Graph images. Point it at a public page and it
reports the page's preview metadata, the per-platform
previews, and any problems it finds, with suggestions
for fixing them. It can render a 1200x630 OG image from
one of the workspace's templates, design a fresh
template from a site's own brand, mint short links that
carry their own previews, report how those links are
being clicked, and force the social platforms to
re-fetch a page whose tags have just changed.

The bridge keeps no preview data 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.
Everything here acts on the caller's own Shareglow
workspace or on public pages the caller names; there
is no sending, payment, or messaging tool in the
surface.

## Tools

- `scan_url` — scan a public page and report its
  link-preview (Open Graph / Twitter Card) metadata,
  previews per platform, and issues with fix
  suggestions. Required: `url`.
- `generate_og_image` — render a 1200x630 Open Graph
  image from a template. Required: `templateId`.
  Optional: `params` (text values such as title and
  subtitle) and `exp` (Unix seconds; makes the signed
  URL expire, paid plans). Returns the permanent image
  URL and whether it was already cached.
- `create_template_from_url` — use AI to design a new
  OG image template from a website's brand (logo,
  colors, fonts). Required: `url`. Returns the chosen
  layoutId, the variables to pass, and the extracted
  brand kit.
- `list_templates` — list the OG image templates the
  workspace can render (built-in and custom) with id,
  name, version and dimensions. Takes no arguments;
  call it before `generate_og_image` to pick a
  templateId.
- `create_short_link` — create a short link with its
  own link preview. Required: `destination`. Optional:
  `slug` and up to three A/B `variants`. Returns id,
  shortUrl and variants.
- `get_link_stats` — get click analytics for a short
  link: totals plus breakdowns by day, country,
  device, browser and referrer. Required: `linkId`.
  Optional: `from` / `to` dates (YYYY-MM-DD).
- `refresh_preview` — force social platforms to
  re-fetch a page's link preview after its OG tags or
  image changed. Required: `url`.

## Configuration

- `SHAREGLOW_MCP_URL` (optional) — override the
  upstream endpoint. Defaults to
  `https://mcp.getshareglow.com/mcp`. (The override
  hook is this rebuild's own labelled reconstruction.)
- `SHAREGLOW_API_KEY` (optional) — when set, every
  upstream request carries an
  `Authorization: Bearer <key>` header, for the
  caller's own Shareglow key (an `sk_live_...` key
  created in the caller's Shareglow dashboard). When
  it is not set, no key header is sent. (The header
  name and the Bearer template are pinned by the
  original's registry record; forwarding the key from
  this env var is 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 `previewglow`), 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 `previewglow error:` (this rendering
is this rebuild's own labelled reconstruction).

## CLI

Each tool is also a subcommand taking one JSON
argument string:

```bash
npx @reneturcios/previewglow scan_url '{"url":"https://example.com/landing"}'
npx @reneturcios/previewglow get_link_stats '{"linkId":"lnk_abc-123"}'
npx @reneturcios/previewglow --version
```

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

## MCP server

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

MCP client config:

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

## Docker

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