What is Webhook?

Unlike traditional polling where a system continuously asks for updates, webhooks enable push-based communication where the source system proactively notifies the destination when something happens. Webhooks consist of a URL endpoint provided by the receiving application and a set of trigger events defined on the sending application. When a trigger event fires, the sender makes an HTTP POST request containing event data to the registered webhook URL, enabling instant communication between systems.

Webhooks are critical infrastructure for AI agents and MCP servers because they enable real-time integration with external systems and event-driven architectures. An AI agent monitoring a customer support system can use webhooks to immediately react to incoming tickets without constant API polling, reducing latency and computational overhead. MCP servers often expose webhook capabilities to allow AI agents to register callbacks for important events, creating responsive automation workflows. This event-driven approach is essential when building scalable multi-agent systems that need to coordinate actions across distributed services, relates to asynchronous processing patterns, and significantly improves responsiveness compared to synchronous request-response models.

From a practical standpoint, implementing webhooks requires careful attention to security, reliability, and error handling. Developers must implement signature verification to ensure webhook requests actually originated from the claimed source, use exponential backoff for retries when delivery fails, and maintain idempotency to handle duplicate deliveries safely. MCP servers should support webhook management endpoints for registering, updating, and unregistering callbacks, while AI agents consuming webhooks need robust queue systems to process events reliably even under high load. Proper webhook implementation directly impacts the stability and trustworthiness of AI agent systems, making it a foundational concept alongside API design and message queue systems.