You can add meta tags to your pages using <Pages.Head />:

<Pages.Head>
  <title> {"My title"->React.string} </title>
  <meta name="description" content="Helloworld">
</Pages.Head>

You can also add scripts & style elements:

<Pages.Head>
  <script> {"console.log('hello')"->React.string} </script>
  <style> {"body {padding: 0}"->React.string} </style>
</Pages.Head>