diff --git a/cpp/README.md b/cpp/README.md
index 08c65400eb5db6527e63e24fa55abe4c640f1436..6e81b567ffd15b94fb6cd61b3a162723f933703d 100644
--- a/cpp/README.md
+++ b/cpp/README.md
@@ -121,9 +121,15 @@ $ sudo apt-get install clang-tidy clang-format
 
 $ rm cmake_build/CMakeCache.txt
 ```  
+Check code style
 ```shell
 $ ./build.sh -l
 ```
+To format the code
+```shell
+$ cd cmake_build
+$ make clang-format
+```
 
 ##### Run unit test
 
diff --git a/cpp/build-support/lint_exclusions.txt b/cpp/build-support/lint_exclusions.txt
index 6888dfa32cc2a592db774451bd85bf7783aa4b71..6ac690f661f56473d28d1bf476ccef9d7a944c81 100644
--- a/cpp/build-support/lint_exclusions.txt
+++ b/cpp/build-support/lint_exclusions.txt
@@ -5,4 +5,5 @@
 *thirdparty*
 *easylogging++*
 *SqliteMetaImpl.cpp
-*src/grpc*
\ No newline at end of file
+*src/grpc*
+*milvus/include*
\ No newline at end of file
diff --git a/cpp/src/utils/ValidationUtil.cpp b/cpp/src/utils/ValidationUtil.cpp
index 254f46f23d7b5f7ef4495552300d056166f0fd60..4345ebb704ede7206742dbe2b0c318f0b5e36f9e 100644
--- a/cpp/src/utils/ValidationUtil.cpp
+++ b/cpp/src/utils/ValidationUtil.cpp
@@ -99,7 +99,7 @@ ValidationUtil::ValidateTableIndexType(int32_t index_type) {
 Status
 ValidationUtil::ValidateTableIndexNlist(int32_t nlist) {
     if (nlist <= 0) {
-        std::string msg = "Invalid nlist value: " + std::to_string(nlist);
+        std::string msg = "nlist value should be greater than 0";
         SERVER_LOG_ERROR << msg;
         return Status(SERVER_INVALID_INDEX_NLIST, msg);
     }
@@ -132,7 +132,7 @@ ValidationUtil::ValidateTableIndexMetricType(int32_t metric_type) {
 Status
 ValidationUtil::ValidateSearchTopk(int64_t top_k, const engine::meta::TableSchema& table_schema) {
     if (top_k <= 0 || top_k > 2048) {
-        std::string msg = "Invalid top k value: " + std::to_string(top_k);
+        std::string msg = "Invalid top k value: " + std::to_string(top_k) + ", rational range [1, 2048]";
         SERVER_LOG_ERROR << msg;
         return Status(SERVER_INVALID_TOPK, msg);
     }
@@ -143,7 +143,8 @@ ValidationUtil::ValidateSearchTopk(int64_t top_k, const engine::meta::TableSchem
 Status
 ValidationUtil::ValidateSearchNprobe(int64_t nprobe, const engine::meta::TableSchema& table_schema) {
     if (nprobe <= 0 || nprobe > table_schema.nlist_) {
-        std::string msg = "Invalid nprobe value: " + std::to_string(nprobe);
+        std::string msg = "Invalid nprobe value: " + std::to_string(nprobe) + ", rational range [1, " +
+                          std::to_string(table_schema.nlist_) + "]";
         SERVER_LOG_ERROR << msg;
         return Status(SERVER_INVALID_NPROBE, msg);
     }