Adds or overwrites only the specified tags for the specified resource. When you specify an existing tag key, the value is overwritten with the new value. Each tag consists of a key and an optional value. Tag keys must be unique per resource. For more information about tags, see <a href="https://docs.aws.amazon.com/sms-voice/latest/userguide/phone-numbers-tags.html">Tags </a> in the <i>End User Messaging SMS User Guide</i>.