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# Parameter field

> Learn how to document API parameters with Fern's ParamField component. Format types, requirements, defaults, and descriptions consistently.

The ParamField component documents API parameters and properties with consistent formatting for type, requirements, default values, and descriptions.

## Usage

**`username`** `string` — required

The user's display name

---

**`limit`** `number` — default: 50

Maximum number of items to return

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**`Markdown`**

```jsx Markdown
<ParamField path="username" type="string" required={true}>
  The user's display name
</ParamField>

<ParamField path="limit" type="number" default="50">
  Maximum number of items to return
</ParamField>
```

## Variants

### Deprecated parameter

**`api_key`** `string` — deprecated

Use OAuth authentication instead

---

**`Markdown`**

```jsx Markdown
<ParamField path="api_key" type="string" deprecated={true}>
  Use OAuth authentication instead
</ParamField>
```

### Union types

**`status`** `'active' | 'inactive' | 'pending'` — default: active

The current status of the user account

---

**`Markdown`**

```jsx Markdown
<ParamField path="status" type="'active' | 'inactive' | 'pending'" default="active">
  The current status of the user account
</ParamField>
```

## Properties

**`path`** `string`

The name of the parameter (e.g., "username", "limit")

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**`type`** `string` — required

The data type of the parameter (e.g., "string", "number", "boolean")

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**`required`** `boolean`

Indicates if the parameter is required. Displays a "Required" label when true.

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**`default`** `string`

The default value for the parameter, if any

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**`deprecated`** `boolean`

Marks the parameter as deprecated.

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**`toc`** `boolean`

Whether to include the parameter in the table of contents. Defaults to `false`.

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