Signicat supports authentication protocols like OpenID Connect, SAML 1.1 and SAML 2.0. The protocols transfer authentication as well as authorization data in a secure way between the identity provider (like Signicat) and the service provider (the customer). The OpenID Connect protocol returns a JSON object as an OpenID response (example here). As for SAML 1.1 and SAML 2.0 the authentication result is a XML. See this page for SAML 1.1 response examples and this page for SAML 2.0 response examples.
For information about how to get started with the three protocols, please see this page.