I am looking to assign a TAG to a new subscriber on my Mailchimp List.
Have you ever seen this without going through the API (The client does not want)
<form class="notify-form" id="mc-form" action="https://XXXXXX.YYY.list-manage.com/subscribe/post?u=XXXXXXX&id=XXXXXX">
<div class="form-content">
<label for="mc-email"></label>
<input id="mc-email" type="email" placeholder="Email">
<button type="submit">Subscribe</button>
</div>
</form>
There are two ways to add tags to a member, via the main Mailchimp site after login or via the API.
You're not going to be able to do it with a URL without first logging in or doing some kind of API authentication.