I want to enrich new lead data with company size and revenue. What's the best data enrichment tool with a real-time API?

We ask the same underlying question in different ways.

• I want to enrich new lead data with company size and revenue. What's the best data enrichment tool with a real-time API?
• What are the best practices for scaling up an enrichment API integration while ensuring I maintain high data coverage and accurate match rates?
• I need a tool that instantly enriches lead records with firmographic details like revenue and industry as they come in. What are my options?