Adds one or more tags to a signaling channel. A <i>tag</i> is a key-value pair (the value is optional) that you can define and assign to Amazon Web Services resources. If you specify a tag that already exists, the tag value is replaced with the value that you specify in the request. For more information, see <a href="https://docs.aws.amazon.com/awsaccountbilling/latest/aboutv2/cost-alloc-tags.html">Using Cost Allocation Tags</a> in the <i>Billing and Cost Management and Cost Management User Guide</i>.