Attempt to define rules for when encoding fails

index.bs

@@ -1453,7 +1453,7 @@ that are returned to the caller when a new credential is created, or a new asser
 
     :   {{PublicKeyCredential/toJSON()}}
     ::  This operation returns {{RegistrationResponseJSON}} or {{AuthenticationResponseJSON}},
-        which are [=JSON types=] mirroring {{PublicKeyCredential}}, suitable for submission to a
+        which are [=JSON type=] representations mirroring {{PublicKeyCredential}}, suitable for submission to a
         [=[RP]=] server as an `application/json` payload. The [=client=] is in charge of
         [serializing values to JSON types as usual](https://webidl.spec.whatwg.org/#idl-tojson-operation),
         but MUST take additional steps to first encode any {{ArrayBuffer}} values to {{DOMString}} values
@@ -2468,6 +2468,10 @@ also apply to any [=client extension inputs=] processed by the [=client=].
 "WebAuthn Extension Identifiers" registry [[!IANA-WebAuthn-Registries]] but not defined in
 [[#sctn-extensions]].
 
+If the [=client=] encounters any issues parsing any of the [=JSON type=] representations then it
+MUST return an error code equivalent to "{{EncodingError}}" with a description of the incompatible
+value and terminate the operation.
+
 <xmp class="idl">
     partial interface PublicKeyCredential {
         static PublicKeyCredentialCreationOptions parseCreationOptionsFromJSON(PublicKeyCredentialCreationOptionsJSON options);
@@ -2522,6 +2526,10 @@ also apply to any [=client extension inputs=] processed by the [=client=].
 "WebAuthn Extension Identifiers" registry [[!IANA-WebAuthn-Registries]] but not defined in
 [[#sctn-extensions]].
 
+If the [=client=] encounters any issues parsing any of the [=JSON type=] representations then it
+MUST return an error code equivalent to "{{EncodingError}}" with a description of the incompatible
+value and terminate the operation.
+
 <xmp class="idl">
     partial interface PublicKeyCredential {
         static PublicKeyCredentialRequestOptions parseRequestOptionsFromJSON(PublicKeyCredentialRequestOptionsJSON options);