Spacelift, a CI/CD automation tool, offers Custom Inputs feature to integrate security tools in workflows. The integration involves three steps: installing the security tool, running it as part of a hook and saving its output to a json file, and accessing the data in a plan policy. Spacelift supports integrating with various security tools like Tfsec, Checkov, Terrascan, and Kics. These tools can be integrated using runner images or before_init hooks. Custom inputs provide flexibility as they can integrate with any JSON file, allowing users to create powerful policies based on their use case.