Webhooks API Documentation Guide

Alright, so you’ve spent a good chunk of time building, testing, and documenting REST APIs. Feels great, right? But here’s the thing: polling sucks.

Imagine constantly refreshing your email inbox to see if you’ve got mail. Annoying, isn’t it? Well, that’s exactly what happens when clients keep sending GET requests to check if new data is available. Enter webhooks—the solution to avoid being that impatient person hitting “refresh” every five seconds.

Webhooks don’t wait for you to ask. They tell you when something important happens. That’s right—real-time notifications, no unnecessary API calls, and fewer server meltdowns.

What is a Webhook?

A webhook is an event-driven API callback that sends data to a specified URL when something happens in an application. Instead of constantly asking, “Hey, got any updates?”, webhooks just notify your system the moment something changes.

Essentially, webhooks are the instant coffee of APIs—quick, effective, and always ready when you need them.

How Webhooks Work

Webhooks vs REST APIs: What’s the Difference?

REST APIs are like checking in at the airport every 5 minutes to see if your flight is boarding. Webhooks are like getting a text when it’s time to go.

How to Document Webhooks in API References

Since webhooks push data instead of waiting for requests, documenting them requires a slightly different approach than REST APIs. Here are the essential components of comprehensive webhook documentation:

1. Webhook Overview Section

Every webhook documentation should start with a clear overview that explains:

Webhooks allow you to receive real-time notifications when an event occurs in our system. 
Instead of polling our API, you can subscribe to specific events and receive an HTTP POST request 
to your webhook URL when they occur.

2. Webhook URL Setup Documentation

POST https://yourdomain.com/webhooks/order_completed

3. Webhook Event Types

Document all the events that your system can send webhooks for:

Users can subscribe to specific events based on their needs.

4. Webhook Payload Format

The most important part of webhook documentation is describing what data is sent. Always include detailed examples for each event type:

{
  "event": "order.completed",
  "data": {
    "order_id": "12345",
    "customer": {
      "name": "John Doe",
      "email": "john@example.com"
    },
    "total": 49.99,
    "currency": "USD"
  }
}

Content-Type: application/json
X-Signature: a94a8fe5ccb19ba61c4c0873d391e987982fbbd3

For each payload property, provide a detailed explanation in a table format:

Securing Webhooks

Since webhooks are publicly accessible, security is crucial. Anyone could send a fake request to your webhook endpoint, so you must verify webhook authenticity before processing the request.

Signature Verification

Every webhook request should include a signature header. Here’s how to verify it:

import hmac
import hashlib

secret = "your-webhook-secret"
payload = '{"event":"order.completed","data":{"order_id":"12345"}}'
received_signature = "a94a8fe5ccb19ba61c4c0873d391e987982fbbd3"

calculated_signature = hmac.new(
    key=secret.encode(),
    msg=payload.encode(),
    digestmod=hashlib.sha256
).hexdigest()

if calculated_signature == received_signature:
    print("Webhook verified!")
else:
    print("Invalid webhook request.")

Handling Webhook Responses

Most webhook providers will retry failed webhook deliveries 3-5 times with an exponential backoff.

Webhook Best Practices

What’s Next?

Now that you understand how webhooks work and how to document them, you’re ready to implement event-driven architectures in your APIs. In the next chapter, Writing API Documentation, we’ll explore broader techniques for creating effective API documentation.