[prng2021]

I've never used their API but the first google result for Hubspot API is their API reference documentation which starts with:

"HubSpot’s developer platform is a core part of our mission to empower organizations to grow better. Our APIs are designed to enable teams of any shape or size to build robust integrations that help them customize and get the most value out of HubSpot.

All HubSpot APIs are built using REST conventions and designed to have a predictable URL structure. They use many standard HTTP features, including methods (POST, GET, PUT, DELETE) and error response codes. All HubSpot API calls are made under https://api.hubapi.com and all responses return standard JSON."

If it's not actually an API in the traditional sense then that's absolutely awful documentation.