> For the complete documentation index, see [llms.txt](https://help.tillit.cloud/api/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://help.tillit.cloud/api/developer-guides/guide-to-using-activity-api.md).

# Guide to using Activity API

Activities inside TilliT can be more advanced then a simple number or text field. To truly get the most out of the operational efficienies TilliT allows, you'll need to know more about the Activity API used inside our calculation items.