diff --git a/pkg/oidc/introspection.go b/pkg/oidc/introspection.go
index 9cf82655..60cea22c 100644
--- a/pkg/oidc/introspection.go
+++ b/pkg/oidc/introspection.go
@@ -11,6 +11,10 @@ type ClientAssertionParams struct {
 	ClientAssertionType string `schema:"client_assertion_type"`
 }
 
+// IntrospectionResponse implements RFC 7662, section 2.2 and
+// OpenID Connect Core 1.0, section 5.1 (UserInfo).
+// https://www.rfc-editor.org/rfc/rfc7662.html#section-2.2.
+// https://openid.net/specs/openid-connect-core-1_0.html#StandardClaims.
 type IntrospectionResponse struct {
 	Active     bool                `json:"active"`
 	Scope      SpaceDelimitedArray `json:"scope,omitempty"`
diff --git a/pkg/oidc/token.go b/pkg/oidc/token.go
index 20303465..62614caa 100644
--- a/pkg/oidc/token.go
+++ b/pkg/oidc/token.go
@@ -105,6 +105,10 @@ func (a *AccessTokenClaims) UnmarshalJSON(data []byte) error {
 	return unmarshalJSONMulti(data, (*atcAlias)(a), &a.Claims)
 }
 
+// IDTokenClaims extends TokenClaims by further implementing
+// OpenID Connect Core 1.0, sections 3.1.3.6 (Code flow),
+// 3.2.2.10 (implicit), 3.3.2.11 (Hybrid) and 5.1 (UserInfo).
+// https://openid.net/specs/openid-connect-core-1_0.html#toc
 type IDTokenClaims struct {
 	TokenClaims
 	NotBefore       Time   `json:"nbf,omitempty"`
diff --git a/pkg/oidc/userinfo.go b/pkg/oidc/userinfo.go
index 3df8b6a6..caff58e9 100644
--- a/pkg/oidc/userinfo.go
+++ b/pkg/oidc/userinfo.go
@@ -1,5 +1,7 @@
 package oidc
 
+// UserInfo implements OpenID Connect Core 1.0, section 5.1.
+// https://openid.net/specs/openid-connect-core-1_0.html#StandardClaims.
 type UserInfo struct {
 	Subject string `json:"sub,omitempty"`
 	UserInfoProfile