> ## Documentation Index
> Fetch the complete documentation index at: https://mintlify.com/iii-hq/iii/llms.txt
> Use this file to discover all available pages before exploring further.

# RegisterTrigger

> Register a trigger to automatically invoke a function

## Request

Register a trigger that will automatically invoke a function when certain conditions are met.

<ParamField name="type" type="string" required>
  Message type. Must be `"registertrigger"`.
</ParamField>

<ParamField name="id" type="string" required>
  Unique identifier for this trigger instance.
</ParamField>

<ParamField name="trigger_type" type="string" required>
  The type of trigger (e.g., `"http"`, `"cron"`, `"queue"`). Must match a registered trigger type.
</ParamField>

<ParamField name="function_id" type="string" required>
  The ID of the function to invoke when this trigger fires. Must match a registered function.
</ParamField>

<ParamField name="config" type="object" required>
  Trigger-specific configuration. The structure depends on the `trigger_type`.

  For example, an HTTP trigger might include routing configuration, while a cron trigger would include a schedule expression.
</ParamField>

## Response

The framework responds with a `TriggerRegistrationResult` message.

<ResponseField name="type" type="string">
  Message type. Will be `"triggerregistrationresult"`.
</ResponseField>

<ResponseField name="id" type="string" required>
  The trigger ID from the request.
</ResponseField>

<ResponseField name="trigger_type" type="string" required>
  The trigger type from the request.
</ResponseField>

<ResponseField name="function_id" type="string" required>
  The function ID from the request.
</ResponseField>

<ResponseField name="error" type="object">
  Error details if registration failed. Omitted if successful.

  <Expandable title="properties">
    <ResponseField name="code" type="string" required>
      Machine-readable error code (e.g., `"trigger_type_not_found"`, `"invalid_config"`, `"function_not_found"`).
    </ResponseField>

    <ResponseField name="message" type="string" required>
      Human-readable error message describing what went wrong.
    </ResponseField>
  </Expandable>
</ResponseField>

## Examples

### HTTP Trigger Registration

**Request:**

```json theme={null}
{
  "type": "registertrigger",
  "id": "http_webhook_handler",
  "trigger_type": "http",
  "function_id": "process_webhook",
  "config": {
    "path": "/webhooks/github",
    "method": "POST"
  }
}
```

**Success Response:**

```json theme={null}
{
  "type": "triggerregistrationresult",
  "id": "http_webhook_handler",
  "trigger_type": "http",
  "function_id": "process_webhook"
}
```

### Cron Trigger Registration

**Request:**

```json theme={null}
{
  "type": "registertrigger",
  "id": "daily_report",
  "trigger_type": "cron",
  "function_id": "generate_report",
  "config": {
    "schedule": "0 9 * * *",
    "timezone": "America/New_York"
  }
}
```

**Success Response:**

```json theme={null}
{
  "type": "triggerregistrationresult",
  "id": "daily_report",
  "trigger_type": "cron",
  "function_id": "generate_report"
}
```

### Queue Trigger Registration

**Request:**

```json theme={null}
{
  "type": "registertrigger",
  "id": "email_queue_processor",
  "trigger_type": "queue",
  "function_id": "send_email",
  "config": {
    "queue_name": "email_queue",
    "batch_size": 10,
    "visibility_timeout": 30
  }
}
```

**Success Response:**

```json theme={null}
{
  "type": "triggerregistrationresult",
  "id": "email_queue_processor",
  "trigger_type": "queue",
  "function_id": "send_email"
}
```

## Error Cases

### Trigger Type Not Found

**Request:**

```json theme={null}
{
  "type": "registertrigger",
  "id": "my_trigger",
  "trigger_type": "nonexistent_type",
  "function_id": "my_function",
  "config": {}
}
```

**Error Response:**

```json theme={null}
{
  "type": "triggerregistrationresult",
  "id": "my_trigger",
  "trigger_type": "nonexistent_type",
  "function_id": "my_function",
  "error": {
    "code": "trigger_type_not_found",
    "message": "No trigger type registered with ID 'nonexistent_type'"
  }
}
```

### Function Not Found

**Request:**

```json theme={null}
{
  "type": "registertrigger",
  "id": "my_trigger",
  "trigger_type": "http",
  "function_id": "nonexistent_function",
  "config": {
    "path": "/test"
  }
}
```

**Error Response:**

```json theme={null}
{
  "type": "triggerregistrationresult",
  "id": "my_trigger",
  "trigger_type": "http",
  "function_id": "nonexistent_function",
  "error": {
    "code": "function_not_found",
    "message": "No function registered with ID 'nonexistent_function'"
  }
}
```

### Invalid Configuration

**Request:**

```json theme={null}
{
  "type": "registertrigger",
  "id": "cron_trigger",
  "trigger_type": "cron",
  "function_id": "my_function",
  "config": {
    "schedule": "invalid cron expression"
  }
}
```

**Error Response:**

```json theme={null}
{
  "type": "triggerregistrationresult",
  "id": "cron_trigger",
  "trigger_type": "cron",
  "function_id": "my_function",
  "error": {
    "code": "invalid_config",
    "message": "Invalid cron expression: 'invalid cron expression'"
  }
}
```

### Duplicate Trigger ID

**Error Response:**

```json theme={null}
{
  "type": "triggerregistrationresult",
  "id": "existing_trigger",
  "trigger_type": "http",
  "function_id": "my_function",
  "error": {
    "code": "duplicate_trigger_id",
    "message": "A trigger with ID 'existing_trigger' is already registered"
  }
}
```

## Notes

* Trigger IDs must be unique within a worker session
* The function must be registered before registering a trigger for it
* The trigger type must be registered (via `RegisterTriggerType`) before use
* Configuration structure is specific to each trigger type
* Successful registration returns a result without an `error` field
* Failed registration returns a result with an `error` field and no exception is thrown