For AI agents

Coding agents such as Claude Code, Codex or Cursor add the subscribe button or a whole integration in minutes when they have the right sources.

Copy-prompt: add the button

Replace the calendar id and give the prompt to your agent:

Add a subscribe button for my calendar cal_XXXXXXXXXXXX to my website.

Use this snippet from Kalender Sync:
<div class="ks-subscribe" data-calendar="cal_XXXXXXXXXXXX"></div>
<script src="https://app.kalender-sync.de/embed/v1/button.js" async></script>

- Place the button where visitors see our events.
- Match the color to our brand color with data-color="#rrggbb".
- Include the script only once per page.
- If the site has a Content Security Policy, allow script-src https://app.kalender-sync.de.
- If the site renders content later (SPA, page builder), call window.KalenderSync?.mountButtons() afterwards.
- If we use our own analytics, track clicks through the ks:subscribe event (event.detail.app).

Docs: https://docs.kalender-sync.de/en/api/button/

Copy-prompt: build an integration

Build an integration that sends our events to the Kalender Sync Publisher API.

- OpenAPI: https://api.kalender-sync.de/v1/openapi.json
- Docs: https://docs.kalender-sync.de/en/api/ (Markdown: page URL without the trailing slash plus .md)
- Authentication: Authorization: Bearer <API key>. Store the key server side only, never in the frontend.
- Write events with PUT /v1/publisher/calendars/{calendar_id}/events/{external_id}; external_id is our own id.
- On delete or unpublish, DELETE the same path.
- Use the full sync for the first import and a daily reconciliation (syncs, batch with sync_id, complete).
- Errors are application/problem+json; branch on "code", not on "detail".
- On 429, respect the Retry-After header.
- Test with a sandbox key (ks_test_) first.

Sources for agents

• OpenAPI 3.1: https://api.kalender-sync.de/v1/openapi.json, public, no key.
• Every docs page as Markdown: append .md to the URL without the trailing slash, for example https://docs.kalender-sync.de/en/api/events.md. Every page also has “Copy Markdown” at the top.
• Everything at once: llms.txt and llms-full.txt.
• Error codes: the type field of every error response links straight to the matching explanation. → Errors

Subscribe calendars through MCP

Through the Kalender Sync MCP server, your AI assistant maintains subscribe calendars without an API key. How to connect an assistant: Connect an AI assistant.

• Unlock: when connecting, actively tick “Manage subscribe calendars (optional)”. It is never preselected. If your assistant is already connected, reconnect it once and tick the box; existing connections never get this permission automatically. This works with Claude and ChatGPT (including Claude Code and Codex). Clients with an access key use the Publisher API instead.
• Tools: list_publisher_calendars, create_publisher_calendar, update_publisher_calendar, write_publisher_events (up to 100 events per call, result per event), list_publisher_events, get_publisher_stats and get_subscribe_button.
• Test mode and live: the assistant creates new calendars in test mode. It creates a live calendar only when you explicitly want it, from Basic on and after your one-time consent to the additional terms. Without it you get terms_required with the link to the settings.
• Deleting: the assistant can delete events, not a whole calendar. That only works through the API.
• Cost: the tools cost no credits.