Clearbit has effectively utilized free products as a strategic marketing approach to drive inbound leads and promote their paid offerings, particularly in the API business where the decision-making process often involves multiple stakeholders beyond just developers. By offering free tools that demonstrate the potential of their APIs, such as the Logo API and Autocomplete API, Clearbit has successfully attracted 100,000 inbound leads and secured deals with major clients. These tools are designed to provide immediate value and simple user experiences, broadening the appeal beyond technical users and engaging product managers, designers, and marketers. This method of "engineering as marketing" not only boosts brand awareness through platforms like Hacker News and Product Hunt but also establishes long-term customer relationships by showcasing Clearbit's core value proposition. By creating apps like Clearbit Connect, which provides enriched contact information within Gmail, Clearbit has expanded its reach to non-developer audiences, particularly salespeople, further driving adoption and integration of their API products. This approach aligns with the concept of providing valuable tools to prospective customers, generating sustainable leads, and enhancing brand visibility over time.