Hi,

Yes, it's possible to check-in and check-out in the Attendance module via API.

You can achieve this by interacting with the hr.attendance model using either XML-RPC or JSON-RPC. You'd typically use the attendance_manual method to toggle between check-in and check-out states based on the current user's last attendance record.

Another approach is to create a custom controller in Odoo that exposes an endpoint (e.g., /api/attendance/checkin) which your external app (mobile, website, etc.) can call. This gives you more flexibility, especially if you want to apply additional business logic or handle authentication differently.

Make sure that the external application authenticates the user properly and has access rights to create or update records in the hr.attendance model.

Hope this helps!