# Webhook (/workflows/blocks/webhook)





The **Webhook block** sends an HTTP POST to an external endpoint. It is an outbound action; the [Webhook trigger](/workflows/triggers/webhook) receives requests that start a run.

<BlockPreview type="webhook" />

## Notify an external service [#notify-an-external-service]

<WorkflowPreview workflow="WEBHOOK_NOTIFY_WORKFLOW" />

Send the Agent's result as a JSON payload to a Slack incoming webhook or your own endpoint. Use the payload format required by that endpoint.

## Configuration [#configuration]

| Field | Behavior |
| - | - |
| **Webhook URL** | Static endpoint URL or a value assembled from earlier outputs. |
| **Payload** | JSON request body. The AI wand can help generate it. |
| **Signing Secret** | Optional `{{WEBHOOK_SECRET}}` or another secret reference for HMAC-SHA256 signing. |
| **Additional Headers** | Key-value headers merged over the automatic headers. |

```json
{
  "event": "workflow.completed",
  "data": {
    "result": "<agent.content>"
  }
}
```

### Automatic headers and signing [#automatic-headers-and-signing]

| Header | Value |
| - | - |
| `Content-Type` | `application/json` |
| `X-Webhook-Timestamp` | Unix timestamp in milliseconds |
| `X-Delivery-ID` | UUID for this request |
| `Idempotency-Key` | Same UUID as X-Delivery-ID |
| `X-Webhook-Signature` | When a secret is supplied: `t=<timestamp>,v1=<signature>` |

The signature is the hexadecimal `HMAC-SHA256(secret, "${timestamp}.${body}")`, using the exact request body. Verify that value against `v1` at the destination.

Custom headers can override these defaults. Overriding signing or timestamp headers can break verification. A new request gets a new delivery ID; the key does not deduplicate separate workflow executions automatically.

## Outputs and failures [#outputs-and-failures]

| Reference | Value |
| - | - |
| `<webhook.data>` | Endpoint response body |
| `<webhook.status>` | Successful response's HTTP status |
| `<webhook.headers>` | Response headers |

Non-2xx responses and request failures use the block's error path. Connect the error port when the workflow should recover.

## Send only when a condition passes [#send-only-when-a-condition-passes]

<WorkflowPreview workflow="WEBHOOK_TRIGGER_WORKFLOW" />

Connect the Condition's **if** port to the Webhook to start an external process only for the matching event.

The Webhook block always uses POST. Use [API](/workflows/blocks/api) for another HTTP method, retry controls, or proxy configuration.

## Related docs [#related-docs]

* [Webhook trigger](/workflows/triggers/webhook)
* [API](/workflows/blocks/api)
* [Credentials and secrets](/platform/credentials)