```md
<!-- MyComponent.stories.mdx -->

import { Meta, Story } from '@storybook/addon-docs';

import { INITIAL_VIEWPORTS } from '@storybook/addon-viewport';

import { MyComponent } from './MyComponent.component';

<Meta
  title="MyComponent"
  parameters={{
    viewport: {
      viewports: INITIAL_VIEWPORTS,
      defaultViewport: 'iphone6',
    },
  }}
  component={MyComponent} />

<Story
  name="MyStory"
  parameters={{
    viewport: {
      defaultViewport: 'iphonex',
    }
  }}>
  {{
    template: '<MyComponent></MyComponent>',
  }}
</Story>
```