Some array type custom fields need special handling - how can that be determined from REST metadata?

[Bob Swift OSS (Bob Swift Atlassian Apps)]

Most of the standard custom fields that JIRA ships have meta data that says they are arrays with string values. That normally means you need to provide a JSON array of option ids. Cascade select is a odd case even though it reports the same schema but needs to be handled differently. It has historically been an odd case .  

The trouble is for an arbitrary custom field that reports meta data as "array" and with items of "string" there doesn't seem to be a way to know the format or content of the data that is expected to set the value of the field. Am I missing something here? One would assume meta data would give you enough information to determine that, but it doesn't. Providing an array of values results in an error. How does one create a representation of data for an arbitrary custom field that represents itself as accepting array values but does not? Also, what indication is there that it needs option ids instead of regular strings? This seems like an omission from the metadata available.

For instance, the agile custom fields look like arrays, but don't accept array values:

schema": {
"type": "array",
"items": "string",
"custom": "com.pyxis.greenhopper.jira:gh-epic-link",
"customId": 11261
},

customfield_11261": "ZAGILE-1",

[Bob Swift OSS (Bob Swift Atlassian Apps)]

I opened this issue ACJIRA-568.