The Webflow API gives you access to certain key aspects of a Workspace and the Sites contained within;
See Introduction to the Webflow API.
Some exciting discussions about the possibility of future API expansion. Specifically mentioned was;
Your API Token is generated under Site settings, on the Integrations tab.
WARNING: Make sure to save your API key safely in a password manager. You only get to generate one key, and once you've generated it, you are no longer able to see it. This means if ever need to add a new service, you'll need to re-generate the key, which will invalidate access for all of your existing services until you give them the new key.
When you authorize an application through the API token, it will appear under the Authorized Applications section of the same page.