File Spec are specified in JSON format. They are used in the Generic Resolve and Generic Deploy tasks and in Bamboo Deployment tasks, File Specs are used in the Artifactory Download task, to specify the dependencies to be resolved from Artifactory or artifacts to be deployed to it.
You can use File Specs in one of the following ways:
Manage them in your SCM, and then during the build, have them pulled to the workspace with the other sources. If you choose this option, you should select the "File" option in the "Upload spec source" or "Download spec source" field and specify the relative path to the File Spec in your workspace.
Save the File Spec JSON as part of the job configuration. If you choose this option, you should select the "Job configuration" option in the "Upload spec source" or "Download spec source" field and specify the File Spec JSON content in your workspace in the "File path" field.
You can read the File Spec schema here.