## Add Key

`v1.custom_fields.add_key(**kwargs) -> void`

**post** `/v1/customFields/addKey`

Add a key to the allow list for a given entity. There is a 100 character limit on custom field keys.

### Parameters

- **enforce\_uniqueness:** `bool`

- **entity:** `:alert | :billable_metric | :charge | 15 more`

  - `:alert`

  - `:billable_metric`

  - `:charge`

  - `:commit`

  - `:contract_credit`

  - `:contract_product`

  - `:contract`

  - `:credit_grant`

  - `:customer_plan`

  - `:customer`

  - `:discount`

  - `:invoice`

  - `:plan`

  - `:professional_service`

  - `:product`

  - `:rate_card`

  - `:scheduled_charge`

  - `:subscription`

- **key:** `String`

### Example

```ruby
require "metronome_sdk"

metronome = MetronomeSDK::Client.new(bearer_token: "My Bearer Token")

result = metronome.v1.custom_fields.add_key(enforce_uniqueness: true, entity: :customer, key: "x_account_id")

puts(result)
```