diff --git a/lib/didkit/plc_operation.rb b/lib/didkit/plc_operation.rb
index 05b3788..95ce30b 100644
--- a/lib/didkit/plc_operation.rb
+++ b/lib/didkit/plc_operation.rb
@@ -5,47 +5,50 @@ class PLCOperation
     class FormatError < StandardError
     end
 
-    attr_reader :did, :created_at, :type, :pds_endpoint, :handles
+    attr_reader :json, :did, :created_at, :type, :pds_endpoint, :handles
 
     def initialize(json)
+      @json = json
       @did = json['did']
-      raise FormatError, "Missing DID" if @did.nil?
-      raise FormatError, "Invalid DID" unless @did.is_a?(String) && @did.start_with?('did:')
+      raise FormatError, "Missing DID: #{json}" if @did.nil?
+      raise FormatError, "Invalid DID: #{@did}" unless @did.is_a?(String) && @did.start_with?('did:')
 
       timestamp = json['createdAt']
-      raise FormatError, "Missing createdAt" if timestamp.nil?
-      raise FormatError, "Invalid createdAt" unless timestamp.is_a?(String)
+      raise FormatError, "Missing createdAt: #{json}" if timestamp.nil?
+      raise FormatError, "Invalid createdAt: #{timestamp.inspect}" unless timestamp.is_a?(String)
 
       @created_at = Time.parse(timestamp)
 
       operation = json['operation']
-      raise FormatError, "Missing operation key" if operation.nil?
-      raise FormatError, "Invalid operation data" unless operation.is_a?(Hash)
+      raise FormatError, "Missing operation key: #{json}" if operation.nil?
+      raise FormatError, "Invalid operation data: #{operation.inspect}" unless operation.is_a?(Hash)
 
       type = operation['type']
-      raise FormatError, "Missing type" if type.nil?
+      raise FormatError, "Missing operation type: #{json}" if type.nil?
 
       @type = type.to_sym
       return unless @type == :plc_operation
 
       services = operation['services']
-      raise FormatError, "Missing services key" if services.nil?
-      raise FormatError, "Invalid services data" unless services.is_a?(Hash)
+      raise FormatError, "Missing services key: #{json}" if services.nil?
+      raise FormatError, "Invalid services data: #{services}" unless services.is_a?(Hash)
 
       if pds = services['atproto_pds']
-        raise FormatError, "Invalid PDS data" unless pds.is_a?(Hash)
-        raise FormatError, "Missing PDS type" unless pds['type']
-        raise FormatError, "Invalid PDS type" unless pds['type'] == 'AtprotoPersonalDataServer'
-        raise FormatError, "Missing PDS endpoint" unless pds['endpoint']
-        raise FormatError, "Invalid PDS endpoint" unless pds['endpoint'].is_a?(String) && pds['endpoint'] =~ %r(://)
+        raise FormatError, "Invalid PDS data: #{pds.inspect}" unless pds.is_a?(Hash)
+        raise FormatError, "Missing PDS type: #{pds.inspect}" unless pds['type']
+        raise FormatError, "Invalid PDS type: #{pds['type']}" unless pds['type'] == 'AtprotoPersonalDataServer'
 
-        @pds_endpoint = pds['endpoint']
+        endpoint = pds['endpoint']
+        raise FormatError, "Missing PDS endpoint: #{pds.inspect}" unless endpoint
+        raise FormatError, "Invalid PDS endpoint: #{endpoint}" unless endpoint.is_a?(String) && endpoint =~ %r(://)
+
+        @pds_endpoint = endpoint
       end
 
       if aka = operation['alsoKnownAs']
-        raise FormatError, "Invalid alsoKnownAs" unless aka.is_a?(Array)
-        raise FormatError, "Invalid alsoKnownAs" unless aka.all? { |x| x.is_a?(String) }
-        raise FormatError, "Invalid alsoKnownAs" unless aka.all? { |x| x =~ %r(\Aat://[^/]+\z) }
+        raise FormatError, "Invalid alsoKnownAs: #{aka.inspect}" unless aka.is_a?(Array)
+        raise FormatError, "Invalid alsoKnownAs: #{aka.inspect}" unless aka.all? { |x| x.is_a?(String) }
+        raise FormatError, "Invalid alsoKnownAs: #{aka.inspect}" unless aka.all? { |x| x =~ %r(\Aat://[^/]+\z) }
 
         @handles = aka.map { |x| x.gsub('at://', '') }
       else