In 4.1. verification Element is
”evidence is a JSON array containing information about the evidence the OP used to verify the user's identity as separate JSON objects. Every object contains the property type which determines the type of the evidence. The RP uses this information to process the evidence property appropriately.”
The type elements are also defined in the JSON Schema.
But definition is missing in the corresponding subchapters 184.108.40.206. to 220.127.116.11.