Field Identifiers are a way of unique labeling fields in order to be able to reference them easily using the eversign API. In order to assign a field label, select it and choose "Field Identifier" from the right-click menu. If you do not choose a unique field identifier for a field, eversign will auto-generate one.
Use cases with eversign API
It is a good practice to use field identifiers in your documents and templates since they can be useful for pulling data from the fields or while debugging error messages related to a certain field.
If you are creating the template via the API, simply set the identifiers when creating the template:
"identifier": "firstpersonsignature", "name": "Signature",
Additionally, keep in mind that field identifiers are case-sensitive which means they need to be exactly the same in your request. They should always be stored with their case preserved and compared in a case-sensitive manner.