{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "type": "object",
  "properties": {
    "pd_a": { "type": "number" },
    "pd_b": { "type": "number" },
    "pd_t": { "type": "number" }
  },
  "required": ["pd_a", "pd_b", "pd_t"],
  "additionalProperties": false
}