diff --git a/src/commands/command_instance.cc b/src/commands/command_instance.cc
index f152d82..aa71b0e 100644
--- a/src/commands/command_instance.cc
+++ b/src/commands/command_instance.cc
@@ -12,9 +12,7 @@
 #include "src/commands/command_definition.h"
 #include "src/commands/command_dictionary.h"
 #include "src/commands/command_queue.h"
-#include "src/commands/prop_types.h"
 #include "src/commands/schema_constants.h"
-#include "src/commands/schema_utils.h"
 #include "src/json_error_codes.h"
 #include "src/utils.h"
 
@@ -68,12 +66,12 @@
 CommandInstance::CommandInstance(const std::string& name,
                                  Command::Origin origin,
                                  const CommandDefinition* command_definition,
-                                 const ValueMap& parameters)
+                                 const base::DictionaryValue& parameters)
     : name_{name},
       origin_{origin},
-      command_definition_{command_definition},
-      parameters_{parameters} {
+      command_definition_{command_definition} {
   CHECK(command_definition_);
+  parameters_.MergeDictionary(&parameters);
 }
 
 CommandInstance::~CommandInstance() {
@@ -97,15 +95,15 @@
 }
 
 std::unique_ptr<base::DictionaryValue> CommandInstance::GetParameters() const {
-  return TypedValueToJson(parameters_);
+  return std::unique_ptr<base::DictionaryValue>(parameters_.DeepCopy());
 }
 
 std::unique_ptr<base::DictionaryValue> CommandInstance::GetProgress() const {
-  return TypedValueToJson(progress_);
+  return std::unique_ptr<base::DictionaryValue>(progress_.DeepCopy());
 }
 
 std::unique_ptr<base::DictionaryValue> CommandInstance::GetResults() const {
-  return TypedValueToJson(results_);
+  return std::unique_ptr<base::DictionaryValue>(results_.DeepCopy());
 }
 
 const Error* CommandInstance::GetError() const {
@@ -114,21 +112,13 @@
 
 bool CommandInstance::SetProgress(const base::DictionaryValue& progress,
                                   ErrorPtr* error) {
-  if (!command_definition_)
-    return ReportDestroyedError(error);
-  ObjectPropType obj_prop_type;
-  obj_prop_type.SetObjectSchema(command_definition_->GetProgress()->Clone());
-
-  ValueMap obj;
-  if (!TypedValueFromJson(&progress, &obj_prop_type, &obj, error))
-    return false;
-
   // Change status even if progress unchanged, e.g. 0% -> 0%.
   if (!SetStatus(State::kInProgress, error))
     return false;
 
-  if (obj != progress_) {
-    progress_ = obj;
+  if (!progress_.Equals(&progress)) {
+    progress_.Clear();
+    progress_.MergeDictionary(&progress);
     FOR_EACH_OBSERVER(Observer, observers_, OnProgressChanged());
   }
 
@@ -137,17 +127,9 @@
 
 bool CommandInstance::Complete(const base::DictionaryValue& results,
                                ErrorPtr* error) {
-  if (!command_definition_)
-    return ReportDestroyedError(error);
-  ObjectPropType obj_prop_type;
-  obj_prop_type.SetObjectSchema(command_definition_->GetResults()->Clone());
-
-  ValueMap obj;
-  if (!TypedValueFromJson(&results, &obj_prop_type, &obj, error))
-    return false;
-
-  if (obj != results_) {
-    results_ = obj;
+  if (!results_.Equals(&results)) {
+    results_.Clear();
+    results_.MergeDictionary(&results);
     FOR_EACH_OBSERVER(Observer, observers_, OnResultsChanged());
   }
   // Change status even if result is unchanged.
@@ -171,36 +153,29 @@
 // On success, returns |true| and the validated parameters and values through
 // |parameters|. Otherwise returns |false| and additional error information in
 // |error|.
-bool GetCommandParameters(const base::DictionaryValue* json,
-                          const CommandDefinition* command_def,
-                          ValueMap* parameters,
-                          ErrorPtr* error) {
+std::unique_ptr<base::DictionaryValue> GetCommandParameters(
+    const base::DictionaryValue* json,
+    const CommandDefinition* command_def,
+    ErrorPtr* error) {
   // Get the command parameters from 'parameters' property.
-  base::DictionaryValue no_params;  // Placeholder when no params are specified.
-  const base::DictionaryValue* params = nullptr;
+  std::unique_ptr<base::DictionaryValue> params;
   const base::Value* params_value = nullptr;
   if (json->Get(commands::attributes::kCommand_Parameters, &params_value)) {
     // Make sure the "parameters" property is actually an object.
-    if (!params_value->GetAsDictionary(&params)) {
+    const base::DictionaryValue* params_dict = nullptr;
+    if (!params_value->GetAsDictionary(&params_dict)) {
       Error::AddToPrintf(error, FROM_HERE, errors::json::kDomain,
                          errors::json::kObjectExpected,
                          "Property '%s' must be a JSON object",
                          commands::attributes::kCommand_Parameters);
-      return false;
+      return params;
     }
+    params.reset(params_dict->DeepCopy());
   } else {
     // "parameters" are not specified. Assume empty param list.
-    params = &no_params;
+    params.reset(new base::DictionaryValue);
   }
-
-  // Now read in the parameters and validate their values against the command
-  // definition schema.
-  ObjectPropType obj_prop_type;
-  obj_prop_type.SetObjectSchema(command_def->GetParameters()->Clone());
-  if (!TypedValueFromJson(params, &obj_prop_type, parameters, error)) {
-    return false;
-  }
-  return true;
+  return params;
 }
 
 }  // anonymous namespace
@@ -246,8 +221,8 @@
     return instance;
   }
 
-  ValueMap parameters;
-  if (!GetCommandParameters(json, command_def, &parameters, error)) {
+  auto parameters = GetCommandParameters(json, command_def, error);
+  if (!parameters) {
     Error::AddToPrintf(error, FROM_HERE, errors::commands::kDomain,
                        errors::commands::kCommandFailed,
                        "Failed to validate command '%s'", command_name.c_str());
@@ -255,7 +230,7 @@
   }
 
   instance.reset(
-      new CommandInstance{command_name, origin, command_def, parameters});
+      new CommandInstance{command_name, origin, command_def, *parameters});
 
   if (!command_id->empty())
     instance->SetID(*command_id);
@@ -268,12 +243,9 @@
 
   json->SetString(commands::attributes::kCommand_Id, id_);
   json->SetString(commands::attributes::kCommand_Name, name_);
-  json->Set(commands::attributes::kCommand_Parameters,
-            TypedValueToJson(parameters_).release());
-  json->Set(commands::attributes::kCommand_Progress,
-            TypedValueToJson(progress_).release());
-  json->Set(commands::attributes::kCommand_Results,
-            TypedValueToJson(results_).release());
+  json->Set(commands::attributes::kCommand_Parameters, parameters_.DeepCopy());
+  json->Set(commands::attributes::kCommand_Progress, progress_.DeepCopy());
+  json->Set(commands::attributes::kCommand_Results, results_.DeepCopy());
   json->SetString(commands::attributes::kCommand_State, EnumToString(state_));
   if (error_) {
     json->Set(commands::attributes::kCommand_Error,
diff --git a/src/commands/command_instance.h b/src/commands/command_instance.h
index 5a2ebf7..30ef907 100644
--- a/src/commands/command_instance.h
+++ b/src/commands/command_instance.h
@@ -44,12 +44,12 @@
   };
 
   // Construct a command instance given the full command |name| which must
-  // be in format "<package_name>.<command_name>", a command |category| and
-  // a list of parameters and their values specified in |parameters|.
+  // be in format "<package_name>.<command_name>" and a list of parameters and
+  // their values specified in |parameters|.
   CommandInstance(const std::string& name,
                   Command::Origin origin,
                   const CommandDefinition* command_definition,
-                  const ValueMap& parameters);
+                  const base::DictionaryValue& parameters);
   ~CommandInstance() override;
 
   // Command overrides.
@@ -124,11 +124,11 @@
   // Command definition.
   const CommandDefinition* command_definition_{nullptr};
   // Command parameters and their values.
-  ValueMap parameters_;
+  base::DictionaryValue parameters_;
   // Current command execution progress.
-  ValueMap progress_;
+  base::DictionaryValue progress_;
   // Command results.
-  ValueMap results_;
+  base::DictionaryValue results_;
   // Current command state.
   Command::State state_ = Command::State::kQueued;
   // Error encountered during execution of the command.
diff --git a/src/commands/command_instance_unittest.cc b/src/commands/command_instance_unittest.cc
index 4e208ed..a03e92b 100644
--- a/src/commands/command_instance_unittest.cc
+++ b/src/commands/command_instance_unittest.cc
@@ -7,8 +7,6 @@
 #include <gtest/gtest.h>
 
 #include "src/commands/command_dictionary.h"
-#include "src/commands/prop_types.h"
-#include "src/commands/schema_utils.h"
 #include "src/commands/unittest_utils.h"
 
 namespace weave {
@@ -70,14 +68,12 @@
 }  // anonymous namespace
 
 TEST_F(CommandInstanceTest, Test) {
-  StringPropType str_prop;
-  IntPropType int_prop;
-  ValueMap params;
-  params["phrase"] =
-      str_prop.CreateValue(base::StringValue{"iPityDaFool"}, nullptr);
-  params["volume"] = int_prop.CreateValue(base::FundamentalValue{5}, nullptr);
+  auto params = CreateDictionaryValue(R"({
+    'phrase': 'iPityDaFool',
+    'volume': 5
+  })");
   CommandInstance instance{"robot.speak", Command::Origin::kCloud,
-                           dict_.FindCommand("robot.speak"), params};
+                           dict_.FindCommand("robot.speak"), *params};
 
   EXPECT_TRUE(
       instance.Complete(*CreateDictionaryValue("{'foo': 239}"), nullptr));
@@ -174,25 +170,6 @@
   EXPECT_EQ("command_failed", error->GetCode());
 }
 
-TEST_F(CommandInstanceTest, FromJson_ParamError) {
-  auto json = CreateDictionaryValue(R"({
-    'name': 'robot.speak',
-    'parameters': {
-      'phrase': 'iPityDaFool',
-      'volume': 20
-    }
-  })");
-  ErrorPtr error;
-  auto instance = CommandInstance::FromJson(json.get(), Command::Origin::kCloud,
-                                            dict_, nullptr, &error);
-  EXPECT_EQ(nullptr, instance.get());
-  auto first = error->GetFirstError();
-  EXPECT_EQ("out_of_range", first->GetCode());
-  auto inner = error->GetInnerError();
-  EXPECT_EQ("invalid_parameter_value", inner->GetCode());
-  EXPECT_EQ("command_failed", error->GetCode());
-}
-
 TEST_F(CommandInstanceTest, ToJson) {
   auto json = CreateDictionaryValue(R"({
     'name': 'robot.jump',