Listing Custom Fields
https://api.karmacrm.com/api/v2/settings/custom_fields

Showing fields for a specific resource
https://api.karmacrm.com/api/v2/settings/custom_fields.json
params: "field_for=Contact"

Field For Options
* Contact
* Company
* Case
* Deal

Things to note
* field_id is required
* value is required
* field_type_id is required
* field_parent_id is required (if select or checkbox)

Field Types
SELECT_BOX = 2
CHECK_BOX = 3
TEXT_AREA = 4
TEXT_FIELD = 5
HEADING = 6
DATE = 7
CURRENCY = 8
AUTO_INCREMENT = 9
INTEGER = 10

Text Field Example
contact[field_values][][field_id]=88556&contact[field_values][][value]=slugger&contact[field_values][][field_type_id]=5

Select Box (and checkbox) Example
contact[field_values][][field_type_id]=2contact[field_values][][field_parent_id]=88557&contact[field_values][][field_id]=88558

Field ID = the option or checkbox that you want to add
Field Parent ID = The ID of the parent you are adding it to.

If you had a custom field called Tone as follows
ID Name Parent ID
1 Tone -
2 Friendly 1
3 Unfriendly 1

And were trying to add the field "Friendly" then you would use 2 for the field_id and 1 for the field_parent_id

Like so:
contact[field_values][][field_type_id]=2contact[field_values][][field_parent_id]=1&contact[field_values][][field_id]=2

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