Descriptors are the schema definitions for attributes, defining how those facts are modeled.

They answer: What does residency.country mean, and how is it proven?

Each descriptor defines:

• Allowed types (e.g., ISO country code)
• Minimum proof requirement (e.g., gov-issued vs self-asserted)
• What proof templates it can be used in (e.g., age ≥ X, “lives in EU”)

Examples:

• age
• country_of_residence
• has_driver_license
• owns_nft_collection_X
• is_employee_of[OrgID]
• has_subscription[TierID]

Descriptor Object (conceptual Example)

Descriptors are schemas for attributes. They define allowed formats, who can issue them, how long they are valid, and which proof templates they can be used in.

2.1 Descriptor Definition

Each descriptor has:

{
  "id": "address.country",
  "title": "Country of Residence",
  "category": "address",
  "datatype": "string",
  "format": "ISO-3166-1 alpha-2",
  "required_for": ["residency_check"],
  "allowed_values": null,
  "issuer_requirements": ["government", "trusted_institution"]
}

This is global and public.

Descriptors DO NOT reveal values.