Retrieve selected customer custom fields

When to use this endpoint

Use Customer_getCustomFields when an integration knows the configured custom-field names and needs a compact ordered value vector.

The response does not repeat field names. Keep the request array beside the response or use a fuller customer read when a self-describing object is required.

Authentication and permissions

The request must authenticate with signed API-key fields or a logged-in CRM session. The handler performs no additional page or role-permission check.

The lookup and any write use the authenticated tenant; an ID from another tenant cannot be addressed through this call.

Parameters

Parameter	Type	Required	Description
`id`	Integer string	Yes	Customer to read; it must convert to a positive integer.
`fields`	JSON array or array	Yes	Ordered custom-field names. Signed form requests normally JSON-encode the array. A direct empty PHP array is treated as missing, while the JSON string `[]` decodes successfully.

Example request

$fields = FM_api('Customer_getCustomFields', [
	'id' => '1088',
	'fields' => json_encode(['Service Level', 'External Region']),
]);

Example response

{
  "id": 1088,
  "fields": ["Gold", ""]
}

Missing keys become empty strings. Stored JSON scalar types are otherwise preserved, and duplicate requested names produce duplicate positions.

Errors and unusual responses

Response	Condition
`{"error":"not logged in"}`	No authenticated tenant context is available. Invalid signed credentials can be rejected by the dispatcher before the handler runs.
`{"error":"missing or invalid parameter: id"}`	`id` is absent or invalid.
`{"error":"missing parameter: fields"}`	`fields` is absent, blank, or supplied directly as an empty array.
`{"error":"invalid parameter: fields"}`	A non-array value does not decode to a JSON array.
`{"error":"customer does not exist"}`	No matching customer row exists.

Legacy application errors may be returned with HTTP 200. Check the decoded response for error, not only the HTTP status.

Behaviour and edge cases

The lookup has no active/deleted filter.
The endpoint does not validate names against the configured custom-field definition; unknown names simply return empty strings.
It returns one ordered result with no filtering or pagination.

See it in Fieldmotion

CRM1

CRM1 uses this call when copying a form to another client account from a configured Client ID custom field, and in the customer predictor training workflow. Filter Network requests for Customer_getCustomFields.

CRM2

No direct production CRM2 caller was found.

Related endpoints

Customer_setCustom replaces one key in the stored custom-values object.
Customers_getById can return the complete encoded custom_values field.