| data-key | pk_live_… / pk_test_… | required | Publishable key. Availability + price-hint only — never PII, never money. |
| data-resource | a resource id (uuid) | required | Which resource's calendar to render. |
| data-api-base | an absolute origin | the <script> tag's own origin, else the current page's origin | Override where calendar requests are sent. Only needed when the script is served from a different origin than the API (this page's own case). |
| data-accent | a 6-digit hex color, e.g. #2563eb | #2563eb | Primary accent color. An accessible foreground (white or near-black) is always computed from it, never accepted as separate input. |
| data-radius | a number (px), clamped to 2–16 | 8 | Corner radius of the card, nav buttons, and day cells. |
| data-font | "system" | "serif" | "mono" | system | One of a closed set of on-device font stacks — no webfont is ever fetched. |
| data-density | "comfortable" | "compact" | comfortable | Internal padding density. |
| data-lang | "en" | "id" | en | UI copy language — month/weekday names, nav labels, availability states. |
| data-fallback-contact | an https:, mailto:, or tel: URL | none | Shown only if live availability fails to load, as an alternate way to reach you. Any other URL scheme is dropped with a console warning. |