The mdq-server instance at mdq-beta.incommon.org serves a JSON metadata file satisfying the following schema (compare with JSON schema used by the Shibboleth SP):

{
	"description": "Schema for a list of protocol entities",
	"type": "array",
	"required": true,
	"items": {
		"description": "a single entity",
		"type": "object",
		"required": true,
		"properties": {
			"entityID": {
				"description": "the entity ID is a globally unique, absolute URI",
				"type": "string",
				"required": true
			},
			"registrarID": {
				"description": "the registrar ID is a globally unique, absolute URI",
				"type": "string",
				"required": true
			},
			"roles": {
				"description": "a list of roles for this entity",
				"type": "array",
				"required": true,
				"items": {
					"description": "a single role",
					"type": "object",
					"required": true,
					"properties": {
						"type": {
							"description": "the type of role",
							"type": "string",
							"required": true
						},
						"displayName": {
							"description": "a role-based display name",
							"displayName": "string",
							"required": false
						}
					}
				}
			}
		}
	}
}