The chat completion API reference needs to be updated for the metadata parameter, to reflect the fact that it can only be used in conjunction with "store": true. Setting only the metadata parameter results in the following error:
The 'metadata' parameter is only allowed when 'store' is enabled.
It’s also a bit deceiving, since devs will think that this parameter is somehow used by the model as part of standard API call, e.g. see this topic.
Proposed wording:
Set of 16 key-value pairs that can be attached to an object for use in our model distillation or evals products. This can be useful for storing additional information about the object in a structured format, and querying for objects via API or the dashboard. Keys are strings with a maximum length of 64 characters. Values are strings with a maximum length of 512 characters. Can only be used in conjunction with
"store": true.