How do I pass custom fields using Chat REST API?

Environment:

Chat
Oracle B2C Service - 18D and 19A releases

Resolution:

To pass the custom field in an EstablishSession REST call you will need to include the prefix "c." or "c$" to the name value when passing custom fields.

For example {\"name\" : \"c$location\", \"type\" : \"string\", \"value\" : \"200 Test Parkway Redwood Shores NJ 07036 USA\"}

You can get further information on Chat REST API here.