private com.google.protobuf.SingleFieldBuilderV3<
                com.google.devtools.cloudtrace.v2.TruncatableString,
                com.google.devtools.cloudtrace.v2.TruncatableString.Builder,
                com.google.devtools.cloudtrace.v2.TruncatableStringOrBuilder>
            getDescriptionFieldBuilder() {
          if (descriptionBuilder_ == null) {
            descriptionBuilder_ =
                new com.google.protobuf.SingleFieldBuilderV3<
                    com.google.devtools.cloudtrace.v2.TruncatableString,
                    com.google.devtools.cloudtrace.v2.TruncatableString.Builder,
                    com.google.devtools.cloudtrace.v2.TruncatableStringOrBuilder>(
                    getDescription(), getParentForChildren(), isClean());
            description_ = null;
          }
          return descriptionBuilder_;
        }
<pre>
A user-supplied message describing the event. The maximum length for
the description is 256 bytes.
</pre>

<code>.google.devtools.cloudtrace.v2.TruncatableString description = 1;</code>
java-trace/proto-google-cloud-trace-v2/src/main/java/com/google/devtools/cloudtrace/v2/Span.java