Webhooks

Manage webhook subscriptions for real-time event notifications. All endpoints require authentication.

Create a webhook

POST /v1/webhooks

Creates a new webhook subscription. A signing secret is generated automatically.

Request body

Field	Type	Required	Description
url	string	Yes	HTTPS endpoint to receive webhook deliveries
events	array	Yes	Event types to subscribe to
description	string	No	Human-readable description
enabled	boolean	No	Whether the webhook is active (default: true)

Event types

Event	Description
fiscalization.completed	A transaction was successfully fiscalized
fiscalization.dead_letter	A transaction exceeded max retry attempts

Example

curl -X POST https://api.zyntem.dev/v1/webhooks \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer zyn_test_abc123def456..." \
  -d '{
    "url": "https://example.com/webhooks/zyntem",
    "events": ["fiscalization.completed", "fiscalization.dead_letter"],
    "description": "Production webhook"
  }'

Response 201 Created

{
  "id": "550e8400-e29b-41d4-a716-446655440000",
  "account_id": "7c9e6679-7425-40de-944b-e07fc1f90ae7",
  "url": "https://example.com/webhooks/zyntem",
  "secret": "whsec_a1b2c3d4e5f6...",
  "events": ["fiscalization.completed", "fiscalization.dead_letter"],
  "description": "Production webhook",
  "enabled": true,
  "created_at": "2026-03-09T12:00:00Z"
}

Save your webhook secret

The secret field is returned only on creation (and on secret rotation). Store it securely for verifying webhook signatures.

Errors

Status	Error	Cause
400	url is required	Missing URL
400	invalid url	Malformed URL
400	events is required	Missing events array
400	invalid event type	Unrecognized event type

---

List webhooks

GET /v1/webhooks

Returns all webhook subscriptions for the authenticated account.

Example

curl https://api.zyntem.dev/v1/webhooks \
  -H "Authorization: Bearer zyn_test_abc123def456..."

Response 200 OK

{
  "data": [
    {
      "id": "550e8400-e29b-41d4-a716-446655440000",
      "url": "https://example.com/webhooks/zyntem",
      "events": ["fiscalization.completed", "fiscalization.dead_letter"],
      "description": "Production webhook",
      "enabled": true,
      "created_at": "2026-03-09T12:00:00Z"
    }
  ]
}

---

Get a webhook

GET /v1/webhooks/{id}

Returns a single webhook subscription by ID.

Example

curl https://api.zyntem.dev/v1/webhooks/550e8400-e29b-41d4-a716-446655440000 \
  -H "Authorization: Bearer zyn_test_abc123def456..."

Response 200 OK

Returns a Webhook object (secret is not included).

Errors

Status	Error
404	webhook not found

---

Update a webhook

PATCH /v1/webhooks/{id}

Partially updates a webhook subscription. Only supplied fields are modified.

Request body

Field	Type	Description
url	string	Updated endpoint URL
events	array	Updated event types
description	string	Updated description
enabled	boolean	Enable or disable the webhook

Example

curl -X PATCH https://api.zyntem.dev/v1/webhooks/550e8400-e29b-41d4-a716-446655440000 \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer zyn_test_abc123def456..." \
  -d '{
    "enabled": false
  }'

Response 200 OK

Returns the updated Webhook object.

---

Delete a webhook

DELETE /v1/webhooks/{id}

Deletes a webhook subscription.

Example

curl -X DELETE https://api.zyntem.dev/v1/webhooks/550e8400-e29b-41d4-a716-446655440000 \
  -H "Authorization: Bearer zyn_test_abc123def456..."

Response 204 No Content

No response body.

---

Rotate secret

POST /v1/webhooks/{id}/rotate-secret

Generates a new signing secret for the webhook. The old secret is immediately invalidated.

Example

curl -X POST https://api.zyntem.dev/v1/webhooks/550e8400-e29b-41d4-a716-446655440000/rotate-secret \
  -H "Authorization: Bearer zyn_test_abc123def456..."

Response 200 OK

{
  "secret": "whsec_f6e5d4c3b2a1..."
}

---

Webhook object

Field	Type	Description
id	uuid	Webhook identifier
account_id	uuid	Owning account identifier
url	string	Delivery endpoint URL
events	array	Subscribed event types
description	string	Human-readable description
enabled	boolean	Whether the webhook is active
created_at	datetime	Creation timestamp

Webhook signatures

Every webhook delivery includes two headers for signature verification:

Header	Description
X-Webhook-Timestamp	Unix timestamp of the delivery
X-Webhook-Signature	sha256=<hex> HMAC-SHA256 signature

Verifying signatures

The signature is computed as HMAC-SHA256(secret, "{timestamp}.{body}"):

import hmac
import hashlib

def verify_webhook(secret, timestamp, body, signature):
    expected = hmac.new(
        secret.encode(),
        f"{timestamp}.{body}".encode(),
        hashlib.sha256
    ).hexdigest()
    return hmac.compare_digest(f"sha256={expected}", signature)

const crypto = require("crypto");

function verifyWebhook(secret, timestamp, body, signature) {
  const expected = crypto
    .createHmac("sha256", secret)
    .update(`${timestamp}.${body}`)
    .digest("hex");
  return `sha256=${expected}` === signature;
}

Webhook payload

{
  "event": "fiscalization.completed",
  "entry_id": "550e8400-e29b-41d4-a716-446655440000",
  "transaction_id": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
  "account_id": "7c9e6679-7425-40de-944b-e07fc1f90ae7",
  "status": "completed",
  "attempt": 1,
  "max_attempts": 50,
  "last_error": "",
  "timestamp": "2026-03-09T14:30:05Z"
}

Retry policy

Failed webhook deliveries (non-2xx responses or timeouts) are retried with the following backoff schedule:

Attempt	Delay
1st retry	10 seconds
2nd retry	60 seconds
3rd retry	300 seconds (5 min)
4th retry	600 seconds (10 min)

After all retries are exhausted, a fiscalization.dead_letter event is emitted.

Webhook deliveries have a 10-second timeout per attempt.