<p>A map that contains one or more tag keys and tag values to attach to an X-Ray group or sampling rule. For more information about ways to use tags, see <a href="https://docs.aws.amazon.com/general/latest/gr/aws_tagging.html">Tagging Amazon Web Services resources</a> in the <i>Amazon Web Services General Reference</i>.</p> <p>The following restrictions apply to tags:</p> <ul> <li> <p>Maximum number of user-applied tags per resource: 50</p> </li> <li> <p>Maximum tag key length: 128 Unicode characters</p> </li> <li> <p>Maximum tag value length: 256 Unicode characters</p> </li> <li> <p>Valid values for key and value: a-z, A-Z, 0-9, space, and the following characters: _ . : / = + - and @</p> </li> <li> <p>Tag keys and values are case sensitive.</p> </li> <li> <p>Don't use <code>aws:</code> as a prefix for keys; it's reserved for Amazon Web Services use. You cannot edit or delete system tags.</p> </li> </ul>