code: def metadata_add_description(self):
          
          service_description = {}
          if (self.args.json):
              service_description = json.loads(self.args.json)
          if (self.args.url):
              if "url" in service_description:
                  raise Exception("json service description already contains url field")
              service_description["url"] = self.args.url
          if (self.args.description):
              if "description" in service_description:
                  raise Exception("json service description already contains description field")
              service_description["description"] = self.args.description
          metadata = load_mpe_service_metadata(self.args.metadata_file)
          # merge with old service_description if necessary
          if ("service_description" in metadata):
              service_description = {**metadata["service_description"], **service_description}
          metadata.set_simple_field("service_description", service_description)
          metadata.save_pretty(self.args.metadata_file)
docs: Metadata: add description