You can check an example here in the documentation.
It is the json part:
{
"policy": {
"_meta": {
"description": "used for nginx log",
"project": {
"name": "myProject",
"department": "myDepartment"
}
},
"phases": {
"warm": {
"min_age": "10d",
"actions": {
"forcemerge": {
"max_num_segments": 1
}
}
},
"delete": {
"min_age": "30d",
"actions": {
"delete": {}
}
}
}
}
}