Enhance JPT payload description

draft-ietf-jose-json-proof-token.md

@@ -133,20 +133,29 @@ The following is an example JWP Protected Header that includes a `cid`:
 > Editor's Note: This section is incomplete. Use it only as an indicator of the intended direction.
 
 Application resolves each claim as required when processing the JPT.  Resolution can result in one of three things:
-1. A disclosed JSON value
-2. A custom proof method
-3. A `null` value
+1. A disclosed JSON value.
+1. An indicator that the value was not disclosed.
+1. An algorithm-specific proof method.
 
 ## Disclosed
 
-Always an octet string of valid JSON text.
+A disclosed payloads are represented as a base64url-encoded UTF-encoded octet string
+representing a valid JSON value.
+
+## Undisclosed
+
+The placeholder indicating that a payload was not disclosed is represented as
+a `null` value for the JWP JSON Serialization
+or the empty string value for the JWP Compact Serialization.
 
 ## Proof Methods
 
-* proof methods can be returned instead of a disclosed payload
-* these are generated by the algorithm from information in the JWP's proof value
-* a proof method may be custom based on the capabilities of the algorithm
-* define common proof method types available?
+Proof methods can be returned instead of a disclosed payload.
+These are generated in an algorithm-specific manner from information in the JWP's proof value.
+
+A proof method may be custom based on the capabilities of the algorithm.
+
+* TBD: Describe common proof method types available?
   * range
   * membership
   * time
@@ -205,6 +214,7 @@ for his valuable contributions to this specification.
   [[ To be removed from the final specification ]]
 
   * Update reference to new repository home
+  * Enhance JPT payload description.
 
  -05