get https://api.triathlon.org/v1/courses/categories
The Course Categories method returns a list of cat_ids that may be used in filtering of all course methods via the category_id parameter.
Examples
List all top-level (parent) categories excluding child (sub) categories.
curl --header "apikey: YOUR_APP_KEY" https://api.triathlon.org/v1/courses/categories?child_categories=false
List all technical official categories (cat_id 236)
curl --header "apikey: YOUR_APP_KEY" https://api.triathlon.org/v1/courses/categories?cat_parent_id=236