---
title: CallHandler
description: JSON Schema for the CallHandler action.
---

Invoke a developer-registered JavaScript handler by name.

```json
{
  "type": "object",
  "properties": {
    "action": {
      "const": "callHandler",
      "default": "callHandler",
      "type": "string"
    },
    "handler": {
      "description": "Name of the registered handler function",
      "type": "string"
    },
    "arguments": {
      "additionalProperties": true,
      "type": [
        "object",
        "null"
      ],
      "default": null,
      "description": "Extra arguments passed to the handler"
    }
  },
  "required": [
    "action",
    "handler"
  ]
}
```
