This field stores information, structured as key-value pairs, for your own use and reference, for example a unique identifier for your own system. Do not store personally identifiable information (PII) in this field. In addition, the following constraints apply:

• Keys must be strings of at most 100 characters.
• Values must be strings of at most 512 characters.
• The total size of the extra data must be less than 1kb.

We recommend using a prefix for your keys to avoid collisions with other systems, as data stored in this field is available to all API users with permission to access the underlying object.