Windows

Detected my tool as malware by Microsoft Defender, and I think it is a false positive alert.

First, check it with https://www.virustotal.com/gui/home/upload.
The CLI is https://github.com/VirusTotal/vt-cli

And you still think it is a false-positive detection, report it in https://www.microsoft.com/en-us/wdsi/filesubmission.
You can track the result in https://www.microsoft.com/en-us/wdsi/submissionhistory.

Checking with actual Microsoft Defender in GitHub Action is a hard task. See GH-442, GH-443, GH-851 for detail.