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Webhooks

Send HMAC-signed HTTP webhook notifications from Potato for 7 annotation event types — with exponential backoff retry, admin monitoring, and Python/Node verification.

Webhooks

New in v2.4.0

Webhooks let Potato notify external systems when annotation events occur — without polling. Connect to data pipelines, trigger alerts, update dashboards, or kick off downstream processing automatically.

Overview

Potato sends an HTTP POST request to your configured endpoint whenever a supported event fires. Payloads are JSON and signed with HMAC-SHA256 so you can verify they came from your Potato instance.

Webhook delivery is fully non-blocking — annotation requests are never delayed while webhooks are in flight. Failed deliveries are retried with exponential backoff.

Configuration

Add a webhooks section to your YAML config:

yaml

webhooks:
  enabled: true
  endpoints:
    - name: "my-pipeline"
      url: "https://your-system.example.com/potato-events"
      secret: "your-signing-secret"        # optional but recommended
      events:
        - annotation.created
        - item.fully_annotated
        - task.completed
      active: true
      timeout: 10

Multiple Endpoints

You can configure multiple endpoints, each with different event subscriptions:

yaml

webhooks:
  enabled: true
  endpoints:
    - name: "data-pipeline"
      url: "https://pipeline.example.com/annotations"
      secret: ${WEBHOOK_SECRET_1}
      events:
        - annotation.created
        - item.fully_annotated
    - name: "slack-alerts"
      url: "https://hooks.slack.com/services/..."
      events:
        - task.completed
        - quality.attention_check_failed
    - name: "catch-all"
      url: "https://logging.example.com/potato"
      events:
        - "*"          # subscribe to all events

Event Types

Event	Fires When
`annotation.created`	An annotator submits a label for an instance
`annotation.updated`	An annotator modifies a previously submitted label
`item.fully_annotated`	An instance reaches its required annotation overlap count
`task.completed`	All instances in the task have been fully annotated
`user.phase_completed`	An annotator completes a phase (Solo Mode workflow)
`quality.attention_check_failed`	An annotator fails an attention check
`webhook.test`	Triggered manually via the admin API for testing

Use "*" to subscribe to all current and future event types.

Payload Format

All events share a common envelope:

json

{
  "event_id": "evt_01HXYZ...",
  "event_type": "annotation.created",
  "timestamp": "2026-03-17T14:23:01Z",
  "task_name": "sentiment-study",
  "data": {
    ...
  }
}

`annotation.created` Payload

json

{
  "event_type": "annotation.created",
  "data": {
    "annotator_id": "user123",
    "instance_id": "doc_042",
    "annotation": {
      "sentiment": "positive",
      "confidence": "high"
    },
    "submitted_at": "2026-03-17T14:23:01Z"
  }
}

`item.fully_annotated` Payload

json

{
  "event_type": "item.fully_annotated",
  "data": {
    "instance_id": "doc_042",
    "annotator_count": 3,
    "annotations": [
      {"annotator_id": "user1", "sentiment": "positive"},
      {"annotator_id": "user2", "sentiment": "positive"},
      {"annotator_id": "user3", "sentiment": "neutral"}
    ]
  }
}

`task.completed` Payload

json

{
  "event_type": "task.completed",
  "data": {
    "task_name": "sentiment-study",
    "total_instances": 500,
    "total_annotations": 1500,
    "completed_at": "2026-03-17T15:00:00Z"
  }
}

Verifying Signatures

When a secret is configured, Potato signs each request using Standard Webhooks (HMAC-SHA256). Three headers are included:

Header	Value
`webhook-id`	Unique delivery ID
`webhook-timestamp`	Unix timestamp of delivery
`webhook-signature`	HMAC-SHA256 signature

Python Verification

python

import hmac
import hashlib
import time
 
def verify_webhook(payload_bytes: bytes, headers: dict, secret: str) -> bool:
    webhook_id = headers.get("webhook-id", "")
    timestamp = headers.get("webhook-timestamp", "")
    signature = headers.get("webhook-signature", "")
 
    # Reject stale requests (older than 5 minutes)
    if abs(time.time() - int(timestamp)) > 300:
        return False
 
    signed_content = f"{webhook_id}.{timestamp}.{payload_bytes.decode()}"
    expected = hmac.new(
        secret.encode(),
        signed_content.encode(),
        hashlib.sha256
    ).hexdigest()
 
    return hmac.compare_digest(f"v1,{expected}", signature)

Node.js Verification

javascript

const crypto = require('crypto');
 
function verifyWebhook(payload, headers, secret) {
  const webhookId = headers['webhook-id'];
  const timestamp = headers['webhook-timestamp'];
  const signature = headers['webhook-signature'];
 
  // Reject stale requests
  if (Math.abs(Date.now() / 1000 - parseInt(timestamp)) > 300) {
    return false;
  }
 
  const signedContent = `${webhookId}.${timestamp}.${payload}`;
  const expected = crypto
    .createHmac('sha256', secret)
    .update(signedContent)
    .digest('hex');
 
  return crypto.timingSafeEqual(
    Buffer.from(`v1,${expected}`),
    Buffer.from(signature)
  );
}

Retry Behavior

Failed deliveries (non-2xx response or timeout) are retried automatically:

Attempt	Delay
1 (initial)	Immediate
2	5 seconds
3	30 seconds
4	5 minutes
5	30 minutes
6	1 hour

After 6 failed attempts, the delivery is marked as permanently failed. The retry queue is persisted to SQLite at {output_dir}/.webhooks/webhook_retries.db — pending retries survive server restarts.

Monitoring and Testing

Admin API

Check webhook status and statistics:

bash

# List all webhooks and their delivery statistics
curl -H "X-API-Key: $ADMIN_API_KEY" \
  http://localhost:8000/admin/api/webhooks

Response:

json

{
  "endpoints": [
    {
      "name": "my-pipeline",
      "url": "https://...",
      "events": ["annotation.created"],
      "active": true,
      "stats": {
        "total_emitted": 1240,
        "total_failed": 3,
        "pending_retries": 0,
        "last_success": "2026-03-17T14:23:01Z"
      }
    }
  ]
}

Send a Test Webhook

bash

curl -X POST -H "X-API-Key: $ADMIN_API_KEY" \
  http://localhost:8000/admin/api/webhooks/test \
  -H "Content-Type: application/json" \
  -d '{"endpoint_name": "my-pipeline"}'

This fires a webhook.test event to the named endpoint immediately.

Full Configuration Reference

yaml

webhooks:
  enabled: true
  endpoints:
    - name: string           # unique name for this endpoint
      url: string            # HTTPS URL to POST to
      secret: string         # optional HMAC secret for signature verification
      events:                # list of event types, or ["*"] for all
        - annotation.created
      active: true           # set false to disable without removing
      timeout: 10            # request timeout in seconds (default: 10)
      max_retries: 6         # max retry attempts (default: 6)

Webhooks

Webhooks

Overview

Configuration

Multiple Endpoints

Event Types

Payload Format

annotation.created Payload

item.fully_annotated Payload

task.completed Payload

Verifying Signatures

Python Verification

Node.js Verification

Retry Behavior

Monitoring and Testing

Admin API

Send a Test Webhook

Full Configuration Reference

Further Reading

`annotation.created` Payload

`item.fully_annotated` Payload

`task.completed` Payload