Leadfeeder has a 'Read Only' API available for Premium subscribers.
You can find Leadfeeder API documentation here.
Your personal Leadfeeder API key is available in your personal settings under API. Alternative access it via this link.
You'll need the API key when querying data from Leadfeeder Public API.
NOTE: It's good to know that we default to ten results per query.
You can read about how one company uses the API here!