Keep working on the BeansTag module. One suggestion is to validate if the path exists when submitting a new BeansTag.

We can use drupal_valid_path() to check if a Drupal system URL exists.

if (drupal_valid_path('node/1')) {
  // url exists
} else {
  // url does not exists
}

According to the specification, this function allows dynamic URL checking like

if (drupal_valid_path('user/*', TRUE)) {
  // url exists
} else {
  // url does not exists
}

But the above code DOES NOT work at all. For more information, please refer to the following thread.
drupal_valid_path fails for dynamic paths (e.g. user/% cannot be added to menus)

Another thing you need to pay attention is that this function returns FALSE for path alias. So if you want to validate a URL for both system URL as well as path alias. You may need the following piece of code.

if (!drupal_valid_path($path)) {
  // Not a system URL.
  if (!drupal_lookup_path('source', $path)) {
    // Not a path alias.
    // $path does not exits
  }
}

Done =)

Reference:

• How to check if page exists using page alias in D7?
• Drupal API – drupal_valid_path
• Drupal API – drupal_lookup_path