storybook/docs/snippets/web-components/component-story-custom-params.ts.mdx

```ts
// Button.stories.ts

import type { Meta, StoryObj } from '@storybook/web-components';

const meta: Meta = {
  title: 'Button',
  component: 'demo-button',
};
export default meta;

type Story = StoryObj<typeof Button>;

export const Primary: Story = {
  args: {
    primary: true,
    label: 'Button',
  },
  parameters: {
    backgrounds: {
      values: [
        { name: 'red', value: '#f00' },
        { name: 'green', value: '#0f0' },
        { name: 'blue', value: '#00f' },
      ],
    },
  },
};
```