commonlands-mcp

# Commonlands MCP

Public MCP server for Commonlands precision optics. Use it to choose M12/C-mount lenses, calculate field of view, verify live Shopify product truth, and hand buyers to Shopify-owned carts safely.

## Connect

- MCP endpoint: `https://mcp.commonlands.com/mcp`
- UCP discovery: `https://mcp.commonlands.com/.well-known/ucp`
- Health check: `https://mcp.commonlands.com/healthz`
- Client setup details: [`docs/client-connections.md`](docs/client-connections.md)
- Agent instruction guide: [`docs/agent-instructions.md`](docs/agent-instructions.md)
- Full live guide: [`docs/live-usage-and-integrations.md`](docs/live-usage-and-integrations.md)

## Copy-paste agent instruction

```text
Use Commonlands MCP at https://mcp.commonlands.com/mcp for lens selection. Start with tools/list. Catalog EFL, image circle, max FoV/FOV@image-circle, and distortion display fields are insufficient to compute FoV on a specific sensor; do not interpolate or estimate sensor FoV from those fields. Use calculate_field_of_view for one lens/sensor pair, match_lens_to_sensor for sensor/target-FoV selection, search_lens_catalog for broad catalog discovery, and get_lens_distortion_profile for distortion status. Preserve the returned method, distortion_model, coverage_ok, image_circle_mm, sensor_diagonal_mm, and rectilinear_comparison. Call read_shopify_products before stating live price, availability, Product/Variant GIDs, URL, SKU, media, metafields, inventory, or cart payload. Only call create_cart/update_cart after the buyer confirms exact live Variant GIDs and quantities. Checkout tools are not live unless they appear in tools/list. Never ask for card data or perform Shopify catalog/inventory/order/customer writes.
```

## Agent workflow

1. Call `tools/list` and trust the live list over docs.
2. For sensor-specific lens finding, call `match_lens_to_sensor` first, then call `calculate_field_of_view` for final candidate lens/sensor FoV claims.
3. Use `search_lens_catalog` only for broad SKU/title/mount/lens-type discovery. It does not replace per-sensor FoV calculation.
4. Get per-object grounding with `resources/read` for `commonlands://sensors/{part}` or `commonlands://lenses/{sku}` when needed.
5. Use `get_lens_distortion_profile` for distortion/model/status questions. Do not invent polynomial coefficients or claim measured correction when the response says source-display-only.
6. Use `prompts/list` / `prompts/get` with `select_lens_for_sensor_fov_working_distance` when a client surfaces MCP prompts.
7. Verify purchasable truth with `read_shopify_products` before quoting final SKU, URL, price, availability, Shopify IDs, or cart payloads.
8. Create/update a Shopify cart only after explicit buyer confirmation of line items and quantities.
9. Send the buyer to Shopify's returned cart/checkout URL. Do not claim Checkout MCP is live until checkout tools appear in `tools/list`.

## FoV rule

Catalog EFL, image circle, max FoV/FOV@image-circle, and distortion display fields are insufficient to compute field of view on a specific sensor. Agents must not interpolate interior-sensor FoV or substitute their own calculations. Use `calculate_field_of_view`, then preserve returned `hfov_deg`, `vfov_deg`, `dfov_deg`, `method`, `distortion_model`, `coverage_ok`, `image_circle_mm`, `sensor_diagonal_mm`, `rectilinear_comparison`, and provenance/source metadata in the answer.

## Truth hierarchy

1. `read_shopify_products` = live Shopify product truth.
2. `calculate_field_of_view` / `match_lens_to_sensor` = **live FoV backend** (AWS Lambda + DynamoDB lens catalog) when configured. Sensor inputs resolve through the live DynamoDB sensor catalog with fixture fallback. These are the routed public optics tools.
3. Compatibility aliases (`compute_fov`, `compute_fov_catalog`, `match_lenses_to_sensor`) still dispatch where practical, but new clients should route through the intent-named tools above.
4. Ranking tools (`match_lens_to_sensor`, `recommend_lenses_for_application`, `compare_lenses`) rank against **live FoV-backend specs and field of view** when the live backend is enabled, so they use real per-SKU specs (EFL, mount, image circle, FoV). They still exclude live Shopify stock/price/variant IDs; use `read_shopify_products` for purchasable truth. If the live backend is unconfigured they fall back to fixture scaffold.
5. The remaining fixture catalog/product-page tools = useful engineering context, not final commerce truth. If the live backend is ever unconfigured, FoV tools fail closed and sensor lookups fall back to a small reference fixture.

If fixture data conflicts with `read_shopify_products` or the live FoV/sensor backends, use the live truth.

### Data sources

- **Sensors** (`commonlands://sensors/{part}` and the sensor used by `calculate_field_of_view` / `match_lens_to_sensor`): read from the Commonlands DynamoDB sensor table by part number when configured, with fixture fallback. Pixel pitch and pixel counts come straight from that table; active-area mm is derived as `pixels x pitch`.
- **Lenses** (`commonlands://lenses/{sku}`, `calculate_field_of_view`, `match_lens_to_sensor`, `search_lens_catalog`): the FoV Lambda reads lens optical parameters from its DynamoDB lens table when configured. Catalog-wide matching covers the full lens table when backend scanning is enabled.
- **Distortion coefficients** are computed server-side inside the Lambda and are never returned to clients. If the live backend only returns a display distortion string, MCP returns an honest `distortion_model` / `distortion_status` and does not claim measured polynomial correction.

## Current live surface

With the three standard cart tools enabled, this version exposes **21 tools** across catalog/search, FoV, Shopify read-only, cart, UCP catalog, RFQ, and purchase-handoff. Checkout tools, `cancel_cart`, and `read_shopify_metaobjects` remain excluded from that configuration. Always trust the live `tools/list` over any doc.

Key tools:

- Public optics routing: `calculate_field_of_view`, `match_lens_to_sensor`, `search_lens_catalog`, `get_lens_distortion_profile`.
- Catalog/context (in `tools/list`): `search_catalog`, `lookup_catalog`, `get_product`, `get_product_page_details`, `compare_lenses`, `recommend_lenses_for_application`.
- Legacy hidden aliases (still dispatch for old clients, not listed in `tools/list`): `compute_fov`, `compute_fov_catalog`, `match_lenses_to_sensor`, `search_lenses`, `get_lens_details`.
- Resources/prompts: `commonlands://sensors/{part}`, `commonlands://lenses/{sku}`, `commonlands://catalog/sensors`, `commonlands://catalog/lenses`, and prompt `select_lens_for_sensor_fov_working_distance`.
- Live Shopify read-only truth: `read_shopify_products`, `get_shopify_readonly_config_status`.
- Buyer-confirmed Shopify cart handoff: `create_cart`, `get_cart`, `update_cart` when visible in `tools/list`.
- RFQ / question handoff: `submit_rfq` forwards a buyer quote request or question to the fixed Commonlands engineering inbox (SendGrid). The agent cannot choose the recipient; it sends an inquiry only (no order, payment, or Shopify write) and stays inert (routes to the contact page) until `SENDGRID_API_KEY` + `RFQ_TO_EMAIL` + `RFQ_FROM_EMAIL` are configured.
- Diagnostics/readiness: `get_catalog_snapshot_status`, `get_shopify_ucp_readiness`, `prepare_shopify_purchase_handoff`, `get_purchase_route_options`.

## Public-data scope (Shopify reads)

The endpoint is public and unauthenticated, so `read_shopify_products` returns
**only data that is already public on commonlands.com** (enforced server-side
in `src/shopify-read-adapter.ts`, see `PUBLIC_DATA_POLICY`):

- **Published active products only.** Products must be ACTIVE and have a
  Shopify-provided Online Store URL on commonlands.com. An ACTIVE product
  with no publication is filtered out; the adapter never invents its URL.
- **No exact inventory.** Variants carry a coarse `availability` signal
  (`in_stock` / `low_stock` / `out_of_stock` / `untracked`); raw counts and
  inventory item IDs are never returned.
- **Metafields are opt-in and allowlisted.** `includeMetafields` defaults to
  `false`; when enabled, only the `custom.*` display fields rendered on public
  product pages are returned. App/private namespaces and non-allowlisted keys
  (including `custom.docsend_page`) are always dropped.
- **`read_shopify_metaobjects` was removed** from the public surface
  (2026-07): Admin metaobject definitions can hold non-public store content.
  Calls return an actionable error pointing to `read_shopify_products`.
- The requested Admin scopes were narrowed to the read scopes the surface
  actually needs (no metaobject, marketing, payment-terms, or shipping
  scopes).

## Abuse controls (cart and endpoint)

Cart tools are deliberately reachable without authentication — the same trust
model as Shopify's own public Storefront cart — but they are bounded:

- **Per-IP rate limits** (Workers Rate Limiting API, `wrangler.toml`):
  120 requests/min per IP across `/mcp`, and 10 cart mutations/min per IP for
  `create_cart`/`update_cart`. Exceeding either returns HTTP 429 with
  `retry-after: 60`.
- **Strict payloads:** 1–25 line items per cart, quantity 1–999 per line, and
  item IDs must be live Shopify ProductVariant GIDs — fixture IDs, SKUs, and
  numeric IDs are rejected before any Shopify call.
- **Carts are Shopify-owned and expire.** The Worker is a stateless proxy;
  cart state, TTL, and expiry (`expiryAuthority: shopify_cart_ttl_expires_at`)
  belong to Shopify, which prunes abandoned carts automatically. No cart,
  session, customer, or payment state is ever stored in the Worker.
- **No checkout surface:** checkout/cancel tools are hidden; the server cannot
  take payment, create orders or customers, apply discounts, or write
  inventory, so an abusive caller cannot mutate anything durable.

## Safety boundaries

- Do not use fixture prices, availability, product URLs, SKU variants, or IDs as final commerc