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# iagctl create decorator

Create a new decorator.

For detailed information on creating and using decorators, see [Validate and limit service inputs with decorators](../using-decorators).

The `iagctl create decorator` command creates a decorator in your gateway data store. Decorators use JSON Schema to validate the inputs passed to a service at runtime, letting you control exactly which inputs a service accepts.

## Syntax

```bash
iagctl create decorator <decorator-name> --schema <string> [flags]
```

## JSON Schema overview

Decorators rely on a JSON Schema document to define and validate service inputs. Each service input corresponds to a property in the schema's `properties` object.

The following fields are particularly relevant in Gateway:

| Field                       | Description                                                                                                                                                                                                                                                                                                                                                                                                             |
| :-------------------------- | :---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `type`                      | The data type for the input. Accepts one of the following values: `string`, `number`, `integer`, `object`, `array`, `boolean`, or `null`. For Python script services, properties defined as `boolean` use bare `--set key` syntax at runtime rather than `--set key=value`. For more information, see [Boolean properties in Python script services](../using-decorators#boolean-properties-in-python-script-services). |
| `enum`                      | A limited set of accepted values for the input.                                                                                                                                                                                                                                                                                                                                                                         |
| `x-itential-payload-type`   | For Python script services, set to `file` to have Gateway write a large property value to a temporary file instead of passing it as a CLI argument. Requires `x-itential-payload-target`. For more information, see [Pass large values as files in Python script services](../using-decorators#pass-large-values-as-files-in-python-script-services).                                                                   |
| `x-itential-payload-target` | The name of the environment variable Gateway uses to pass the temporary file path to your script when `x-itential-payload-type` is set to `file`.                                                                                                                                                                                                                                                                       |

For additional validation options, see the [JSON Schema website](https://json-schema.org/draft/2020-12/json-schema-validation).

For example, consider a gateway service that takes two inputs: `interface` and `device_type`. The following JSON Schema document validates those inputs:

```json
{
  "$id": "root",
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "type": "object",
  "properties": {
    "interface": {
      "type": "string",
      "description": "The interface to update"
    },
    "device_type": {
      "type": "string",
      "description": "The type of device",
      "enum": ["ios", "eos", "nxos"]
    }
  },
  "required": [
    "interface",
    "device_type"
  ],
  "additionalProperties": false
}
```

When you specify this decorator on a service, it validates that the `interface` and `device_type` inputs are passed correctly in the `iagctl run service` request:

```bash
iagctl run pythonscript example-service-with-deco \
--set interface=1/1/1 \
--set device_type=eos
```

## Examples

### Create a decorator from a file

To create a decorator from a JSON Schema file called `my_decorator.json`, run the following command:

```bash
iagctl create decorator my-decorator \
--schema @my_decorator.json
```

You typically format schema files as JSON, but Gateway also accepts YAML.

### Create a decorator from inline JSON

You can also specify the JSON Schema content directly in the command. Wrap your JSON in single quotes:

```bash
iagctl create decorator my-decorator \
--schema '{"$id":"root","$schema":"https://json-schema.org/draft/2020-12/schema","type":"object","properties":{"interface":{"type":"string"}}}'
```

## Options

```bash
    --description string   A brief description of the decorator
    -h, --help             Help for decorator
    --schema string        The schema of the decorator. Accepts inline JSON or a file reference prefixed with '@'.
    --tag stringArray      Metadata tag(s) to associate with the decorator
```

## Options inherited from parent commands

```bash
  --profile string   Specify the client profile to use (case-insensitive, defaults to [client] section)
  --config string   Path to the configuration file
  --raw             Display the result of the command in raw format
  --verbose         Enable verbose output
```