Hello - there isn't a built-in scanning tool for ESQL, though the toolkit does a good job of flagging ESQL errors and warnings.
Beyond that, there is a SonarQube ESQL plugin that scans ESQL files and detects issues; some of the issues are opinions, others performance enhancements (like using field references instead of multiple navigations to the same place), etc. Your mileage may vary in how useful you find the results, but it scans ESQL in source projects and will also cover Maven configuration, Java source, and other file types.
App Connect development does not generally endorse third-party tools, and so this is not a recommendation or a support statement, but you may find SonarQube worth exploring. I'm not aware of other tools at the moment.