In addition to a properly configured data type, format mask (for dates), and REST payload selector, you can use the Data Profile Column Additional Info attribute to include a comma-separated list of one or more of the following case-sensitive tag names used to optimize how APEX communicates with the REST Data Source endpoint:

• RemotePK - Omit null remote primary keys from create payloads so the service defaults their values.
• CreateOnly - Exclude column from update payloads.
• ReadOnly - Exclude column from DML payloads.
• HasDefault - Omit a null-valued column from create payload to prioritize the serverside default.
• Required - Not currently enforced but useful to be aware of (and possibly enforced by APEX in the future).