diff --git a/bg/api/ac_chain.proto b/bg/api/ac_chain.proto
index ad8271c..bdb1491 100644
--- a/bg/api/ac_chain.proto
+++ b/bg/api/ac_chain.proto
@@ -11,11 +11,11 @@ option java_multiple_files = true;
 
 service AcChain {
     rpc BlockNumber (BlockNumberRequest) returns (BlockNumberResponse);
-    rpc GetBlockByNumber (GetBlockByNumberRequest) returns (GetBlockByNumberResponse);
-    rpc GetBlockByHash (GetBlockByHashRequest) returns (GetBlockByHashResponse);
-    rpc GetMessageByHash (GetMessageByHashRequest) returns (GetMessageByHashResponse);
-    rpc GetMessageByBlockNumberAndIndex (GetMessageByBlockNumberAndIndexRequest) returns (GetMessageByBlockNumberAndIndexResponse);
-    rpc GetMessageByBlockHashAndIndex (GetMessageByBlockHashAndIndexRequest) returns (GetMessageByBlockHashAndIndexResponse);
+    rpc GetBlockByNumber (GetBlockByNumberRequest) returns (Block);
+    rpc GetBlockByHash (GetBlockByHashRequest) returns (Block);
+    rpc GetMessageByHash (GetMessageByHashRequest) returns (Block);
+    rpc GetMessageByBlockNumberAndIndex (GetMessageByBlockNumberAndIndexRequest) returns (Message);
+    rpc GetMessageByBlockHashAndIndex (GetMessageByBlockHashAndIndexRequest) returns (Message);
 }
 
 message Message {
@@ -57,41 +57,26 @@ message GetBlockByNumberRequest {
     uint64 number = 2;
     bool full_transaction = 3;
 }
-message GetBlockByNumberResponse {
-    Block block = 1;
-}
 
 message GetBlockByHashRequest {
     string ledger = 1;
     bytes hash = 2;
     bool full_transaction = 3;
 }
-message GetBlockByHashResponse {
-    Block block = 1;
-}
 
 message GetMessageByHashRequest {
     string ledger = 1;
     bytes hash = 2;
 }
-message GetMessageByHashResponse {
-    Message message = 1;
-}
 
 message GetMessageByBlockNumberAndIndexRequest {
     string ledger = 1;
     uint64 block_number = 2;
     uint32 index = 3;
 }
-message GetMessageByBlockNumberAndIndexResponse {
-    Message message = 1;
-}
 
 message GetMessageByBlockHashAndIndexRequest {
     string ledger = 1;
     bytes block_hash = 2;
     uint32 index = 3;
 }
-message GetMessageByBlockHashAndIndexResponse {
-    Message message = 1;
-}
diff --git a/bg/api/tx_ledger.proto b/bg/api/tx_ledger.proto
index 53a7790..7f6162f 100644
--- a/bg/api/tx_ledger.proto
+++ b/bg/api/tx_ledger.proto
@@ -2,6 +2,7 @@ syntax = "proto3";
 
 package bg.api;
 
+import "google/protobuf/empty.proto";
 import "bg/api/common.proto";
 
 option go_package = "bg/api/protobuf/tx_ledger";
@@ -11,7 +12,7 @@ option java_multiple_files = true;
 
 service TxLedger {
     rpc CreateLedger (CreateLedgerRequest) returns (CreateLedgerResponse);
-    rpc GetLedgers (GetLedgersRequest) returns (GetLedgersResponse);
+    rpc GetLedgers (google.protobuf.Empty) returns (GetLedgersResponse);
     rpc SendMessage (SendMessageRequest) returns (SendMessageResponse);
 }
 
@@ -22,8 +23,6 @@ message CreateLedgerResponse {
     bool ok = 1;
 }
 
-message GetLedgersRequest {
-}
 message GetLedgersResponse {
     repeated string ledgers = 1;
 }
diff --git a/google/protobuf/empty.proto b/google/protobuf/empty.proto
new file mode 100644
index 0000000..03cacd2
--- /dev/null
+++ b/google/protobuf/empty.proto
@@ -0,0 +1,52 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+syntax = "proto3";
+
+package google.protobuf;
+
+option csharp_namespace = "Google.Protobuf.WellKnownTypes";
+option go_package = "github.com/golang/protobuf/ptypes/empty";
+option java_package = "com.google.protobuf";
+option java_outer_classname = "EmptyProto";
+option java_multiple_files = true;
+option objc_class_prefix = "GPB";
+option cc_enable_arenas = true;
+
+// A generic empty message that you can re-use to avoid defining duplicated
+// empty messages in your APIs. A typical example is to use it as the request
+// or the response type of an API method. For instance:
+//
+//     service Foo {
+//       rpc Bar(google.protobuf.Empty) returns (google.protobuf.Empty);
+//     }
+//
+// The JSON representation for `Empty` is empty JSON object `{}`.
+message Empty {}