diff --git a/core/api/service/child_state/requests/get_keys.cpp b/core/api/service/child_state/requests/get_keys.cpp
index a78a26d3c4..90c7d8e6c0 100644
--- a/core/api/service/child_state/requests/get_keys.cpp
+++ b/core/api/service/child_state/requests/get_keys.cpp
@@ -19,7 +19,7 @@ namespace kagome::api::child_state::request {
     // childKey
     auto &param0 = params[0];
 
-    if (not param0.IsString() or param0.IsNil()) {
+    if (not param0.IsString()) {
       throw jsonrpc::InvalidParametersFault(
           "Parameter '[child_storage_key]' must be a hex string");
     }
@@ -29,7 +29,7 @@ namespace kagome::api::child_state::request {
 
     auto &param1 = params[1];
 
-    if (not param1.IsString() and not param1.IsNil()) {
+    if (not param1.IsString()) {
       throw jsonrpc::InvalidParametersFault(
           "Parameter '[prefix]' must be a hex string");
     }
@@ -48,16 +48,17 @@ namespace kagome::api::child_state::request {
       return outcome::success();
     }
 
-    // process at param
-    if (not params[2].IsString()) {
-      throw jsonrpc::InvalidParametersFault(
-          "Parameter '[at]' must be a hex string representation of an encoded "
-          "optional byte sequence");
+    if (not params[2].IsNil()) {
+      // process at param
+      if (not params[2].IsString()) {
+        throw jsonrpc::InvalidParametersFault(
+            "Parameter '[at]' must be a hex string representation of an "
+            "encoded optional byte sequence");
+      }
+      OUTCOME_TRY(at_span, common::unhexWith0x(params[2].AsString()));
+      OUTCOME_TRY(at, primitives::BlockHash::fromSpan(at_span));
+      at_ = at;
     }
-    OUTCOME_TRY(at_span, common::unhexWith0x(params[2].AsString()));
-    OUTCOME_TRY(at, primitives::BlockHash::fromSpan(at_span));
-    at_ = at;
-
     return outcome::success();
   }
 
diff --git a/core/api/service/child_state/requests/get_keys_paged.cpp b/core/api/service/child_state/requests/get_keys_paged.cpp
index f63aa65c21..fbe4deef75 100644
--- a/core/api/service/child_state/requests/get_keys_paged.cpp
+++ b/core/api/service/child_state/requests/get_keys_paged.cpp
@@ -19,7 +19,7 @@ namespace kagome::api::child_state::request {
     // childKey
     auto &param0 = params[0];
 
-    if (not param0.IsString() or param0.IsNil()) {
+    if (not param0.IsString()) {
       throw jsonrpc::InvalidParametersFault(
           "Parameter '[child_storage_key]' must be a hex string");
     }
@@ -29,7 +29,7 @@ namespace kagome::api::child_state::request {
 
     auto &param1 = params[1];
 
-    if (not param1.IsString() and not param1.IsNil()) {
+    if (not param1.IsString()) {
       throw jsonrpc::InvalidParametersFault(
           "Parameter '[prefix]' must be a hex string");
     }
@@ -69,15 +69,17 @@ namespace kagome::api::child_state::request {
       return outcome::success();
     }
 
-    // process at param
-    if (not params[4].IsString()) {
-      throw jsonrpc::InvalidParametersFault(
-          "Parameter '[at]' must be a hex string representation of an encoded "
-          "optional byte sequence");
+    if (not params[4].IsNil()) {
+      // process at param
+      if (not params[4].IsString()) {
+        throw jsonrpc::InvalidParametersFault(
+            "Parameter '[at]' must be a hex string representation of an encoded "
+            "optional byte sequence");
+      }
+      OUTCOME_TRY(at_span, common::unhexWith0x(params[4].AsString()));
+      OUTCOME_TRY(at, primitives::BlockHash::fromSpan(at_span));
+      at_ = at;
     }
-    OUTCOME_TRY(at_span, common::unhexWith0x(params[4].AsString()));
-    OUTCOME_TRY(at, primitives::BlockHash::fromSpan(at_span));
-    at_ = at;
 
     return outcome::success();
   }
diff --git a/core/api/service/child_state/requests/get_storage.cpp b/core/api/service/child_state/requests/get_storage.cpp
index 87f9b981f5..d147852a6c 100644
--- a/core/api/service/child_state/requests/get_storage.cpp
+++ b/core/api/service/child_state/requests/get_storage.cpp
@@ -14,7 +14,7 @@ namespace kagome::api::child_state::request {
     }
     auto &param0 = params[0];
 
-    if (not param0.IsString() or param0.IsNil()) {
+    if (not param0.IsString()) {
       throw jsonrpc::InvalidParametersFault(
           "Parameter '[child_storage_key]' must be a hex string");
     }
diff --git a/core/api/service/child_state/requests/get_storage_size.cpp b/core/api/service/child_state/requests/get_storage_size.cpp
index a278b2af47..5f62ed1b9c 100644
--- a/core/api/service/child_state/requests/get_storage_size.cpp
+++ b/core/api/service/child_state/requests/get_storage_size.cpp
@@ -14,7 +14,7 @@ namespace kagome::api::child_state::request {
     }
     auto &param0 = params[0];
 
-    if (not param0.IsString() or param0.IsNil()) {
+    if (not param0.IsString()) {
       throw jsonrpc::InvalidParametersFault(
           "Parameter '[child_storage_key]' must be a hex string");
     }
diff --git a/core/api/service/state/requests/call.cpp b/core/api/service/state/requests/call.cpp
index 52aafc0e91..677a990196 100644
--- a/core/api/service/state/requests/call.cpp
+++ b/core/api/service/state/requests/call.cpp
@@ -14,12 +14,12 @@ namespace kagome::api::state::request {
   };
 
   outcome::result<void> Call::init(const jsonrpc::Request::Parameters &params) {
-    if (params.size() > 3 or params.size() < 2) {
+    if (params.size() < 2 or params.size() > 3) {
       throw jsonrpc::InvalidParametersFault("Incorrect number of params");
     }
     auto &param0 = params[0];
 
-    if (param0.IsString() and not param0.IsNil()) {
+    if (param0.IsString()) {
       method_ = param0.AsString();
     } else {
       throw jsonrpc::InvalidParametersFault(
@@ -27,7 +27,7 @@ namespace kagome::api::state::request {
     }
 
     auto &param1 = params[1];
-    if (param1.IsString() and not param1.IsNil()) {
+    if (param1.IsString()) {
       auto encoded_args = common::unhexWith0x(param1.AsString());
       if (encoded_args.has_value()) {
         data_ = common::Buffer(encoded_args.value());
@@ -45,15 +45,17 @@ namespace kagome::api::state::request {
     }
 
     auto &param2 = params[2];
-    // process at param
-    if (not param2.IsString()) {
-      throw jsonrpc::InvalidParametersFault(
-          "Parameter '[at]' must be a hex string representation of an encoded "
-          "optional byte sequence");
+    if (!param2.IsNil()) {
+      // process at param
+      if (not param2.IsString()) {
+        throw jsonrpc::InvalidParametersFault(
+            "Parameter '[at]' must be a hex string representation of an "
+            "encoded optional byte sequence");
+      }
+      OUTCOME_TRY(at_span, common::unhexWith0x(param2.AsString()));
+      OUTCOME_TRY(at, primitives::BlockHash::fromSpan(at_span));
+      at_ = at;
     }
-    OUTCOME_TRY(at_span, common::unhexWith0x(param2.AsString()));
-    OUTCOME_TRY(at, primitives::BlockHash::fromSpan(at_span));
-    at_ = at;
 
     return outcome::success();
   }
diff --git a/core/api/service/state/requests/get_keys_paged.cpp b/core/api/service/state/requests/get_keys_paged.cpp
index 8c1b4d8cf2..557a09f71d 100644
--- a/core/api/service/state/requests/get_keys_paged.cpp
+++ b/core/api/service/state/requests/get_keys_paged.cpp
@@ -11,12 +11,12 @@ namespace kagome::api::state::request {
 
   outcome::result<void> GetKeysPaged::init(
       const jsonrpc::Request::Parameters &params) {
-    if (params.size() > 4 or params.size() <= 1) {
+    if (params.size() > 4 or params.size() < 2) {
       throw jsonrpc::InvalidParametersFault("Incorrect number of params");
     }
     auto &param0 = params[0];
 
-    if (not param0.IsString() and not param0.IsNil()) {
+    if (not param0.IsString()) {
       throw jsonrpc::InvalidParametersFault(
           "Parameter '[prefix]' must be a hex string");
     }
@@ -42,7 +42,6 @@ namespace kagome::api::state::request {
       return outcome::success();
     }
 
-    // process prev_key param
     if (not params[2].IsNil()) {
       if (not params[2].IsString()) {
         throw jsonrpc::InvalidParametersFault(
@@ -57,15 +56,17 @@ namespace kagome::api::state::request {
       return outcome::success();
     }
 
-    // process at param
-    if (not params[3].IsString()) {
-      throw jsonrpc::InvalidParametersFault(
-          "Parameter '[at]' must be a hex string representation of an encoded "
-          "optional byte sequence");
+    if (not params[3].IsNil()) {
+      // process at param
+      if (not params[3].IsString()) {
+        throw jsonrpc::InvalidParametersFault(
+            "Parameter '[at]' must be a hex string representation of an encoded "
+            "optional byte sequence");
+      }
+      OUTCOME_TRY(at_span, common::unhexWith0x(params[3].AsString()));
+      OUTCOME_TRY(at, primitives::BlockHash::fromSpan(at_span));
+      at_ = at;
     }
-    OUTCOME_TRY(at_span, common::unhexWith0x(params[3].AsString()));
-    OUTCOME_TRY(at, primitives::BlockHash::fromSpan(at_span));
-    at_ = at;
 
     return outcome::success();
   }
diff --git a/core/api/service/state/requests/subscribe_storage.cpp b/core/api/service/state/requests/subscribe_storage.cpp
index 26bd20bb04..af59698e79 100644
--- a/core/api/service/state/requests/subscribe_storage.cpp
+++ b/core/api/service/state/requests/subscribe_storage.cpp
@@ -9,8 +9,8 @@ namespace kagome::api::state::request {
 
   outcome::result<void> SubscribeStorage::init(
       const jsonrpc::Request::Parameters &params) {
-    if (params.size() > 1 or params.empty()) {
-      throw jsonrpc::InvalidParametersFault("Incorrect number of params");
+    if (params.size() != 1) {
+      throw jsonrpc::InvalidParametersFault("subscribeStorage takes one parameter");
     }
     auto &keys = params[0];
     if (!keys.IsArray()) {
diff --git a/core/api/service/state/requests/unsubscribe_storage.cpp b/core/api/service/state/requests/unsubscribe_storage.cpp
index 5a09531bed..9f6e0d45f1 100644
--- a/core/api/service/state/requests/unsubscribe_storage.cpp
+++ b/core/api/service/state/requests/unsubscribe_storage.cpp
@@ -9,8 +9,8 @@ namespace kagome::api::state::request {
 
   outcome::result<void> UnsubscribeStorage::init(
       const jsonrpc::Request::Parameters &params) {
-    if (params.size() > 1 or params.empty()) {
-      throw jsonrpc::InvalidParametersFault("Incorrect number of params");
+    if (params.size() != 1) {
+      throw jsonrpc::InvalidParametersFault("unsubscribeStorage takes one parameter");
     }
 
     auto &id = params[0];