We are using the metadata API to access field metadata such as description, data type, default value etc. This is for standard objects but on custom fields e.g.:
SELECT Id, Metadata, TableEnumOrId FROM CustomField WHERE DeveloperName = :fieldName AND TableEnumOrId = :fieldType AND NamespacePrefix = :namespacePrefix
For some customers this fails with
sObject type 'CustomField' is not supported. We have checked the user permissions and they have a System Administrator profile with:
- API Access
- Modify All Data
What is actually needed to access this object?