@redocly/openapi-core/src/rules/common/operation-description.ts

See https://github.com/Redocly/redocly-cli

import { Oas3Rule, Oas2Rule } from '../../visitors';
import { validateDefinedAndNonEmpty } from '../utils';
import { UserContext } from '../../walk';
import { Oas2Operation } from '../../typings/swagger';
import { Oas3Operation } from '../../typings/openapi';

export const OperationDescription: Oas3Rule | Oas2Rule = () => {
  return {
    Operation(operation: Oas2Operation | Oas3Operation, ctx: UserContext) {
      validateDefinedAndNonEmpty('description', operation, ctx);
    },
  };
};