Hello FaCoffee,

Hope you got this sorted already. If not, here are some clarifications that might help,
1. Would a classification be an entity?
No, classifications are not entities. They are like tags associated to an entity. You can have the same classification for multiple entities.
https://learn.microsoft.com/en-us/rest/api/purview/datamapdataplane/entity/add-classification?view=rest-purview-datamapdataplane-2023-09-01&tabs=HTTP

2. If so, how should this JSON be structured for a Custom Classification? For example, what is the right value for typeName?
A custom classification should be created as mentioned here: https://docs.azure.cn/en-us/purview/data-map-classification-custom#steps-to-create-a-custom-classification
You can create classification rules programmatically. Refer to: https://learn.microsoft.com/en-us/rest/api/purview/scanningdataplane/classification-rules/create-or-replace?view=rest-purview-scanningdataplane-2023-09-01&tabs=HTTP

The typeName name should be the custom classification name created? For example, **contoso.hr.employee_ID.
**
Hope this helps!

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