Dialogflow Fulfillment Library provides a structured way to connect your Dialogflow agent to custom backend logic via webhooks. It offers built-in response builders for cards, suggestion chips, quick replies, and payloads, as well as context management and parameter extraction. Developers can define intent handlers in a concise map, leverage middleware for preprocessing, and integrate with Actions on Google for voice applications. Deployment to Google Cloud Functions is straightforward, ensuring scalable, secure, and maintainable conversational services.