How to get value of

How can I get value of in custom query?

I use this: container="${__tags['service_name']} |= ${__trace.traceId}
but have got this result: container="${__tags['service_name']} |= 58173b1b1a524c1abfc94a3c801547c6

As far as I understand ${__span.tags[""]} should work, I see that you are using service_name, try

checkout Configure the Tempo data source | Grafana documentation for more details.