You can add metadata to your transcription using the custom_metadata input during your POST request to /v2/pre-recorded. This helps recognize your transcription when fetching via GET /v2/pre-recorded/:id and enables filtering in GET /v2/pre-recorded. For example: 
"custom_metadata": {
  "internalUserId": 2348739875894375,
  "paymentMethod": { "last4Digits": 4576 },
  "internalUserName": "Spencer"
}
Filter results: 
https://api.gladia.io/v2/pre-recorded?custom_metadata={"internalUserId": "2348739875894375"}
or 
https://api.gladia.io/v2/pre-recorded?custom_metadata={"paymentMethod": {"last4Digits": 4576}, "internalUserName": "Spencer"}
custom_metadata cannot be longer than 2000 characters when stringified.