Our API is documented here: GBIF API Reference :: Technical Documentation (see also here the API for checklist bank which is what’s behind the Catalogue of Life website https://api.checklistbank.org).
I suggest checking these two Data Use Club recoded webinars:
- A general introduction to our API functions
- A webinar specifically about accessing species information (it includes information about checklist bank) and its associated links: Data Use Club Practical Session: accessing and downloading species information