diff --git a/src/mcp/tools.zig b/src/mcp/tools.zig
index f4a82570..4a3dbfc0 100644
--- a/src/mcp/tools.zig
+++ b/src/mcp/tools.zig
@@ -325,7 +325,7 @@ fn handleGoto(server: *Server, arena: std.mem.Allocator, id: std.json.Value, arg
 }
 
 fn handleMarkdown(server: *Server, arena: std.mem.Allocator, id: std.json.Value, arguments: ?std.json.Value) !void {
-    const args = parseArgsOrDefault(UrlParams, arena, arguments);
+    const args = try parseArgsOrDefault(UrlParams, arena, arguments, server, id);
     const page = try ensurePage(server, id, args.url);
 
     const content = [_]protocol.TextContent(ToolStreamingText){.{
@@ -335,7 +335,7 @@ fn handleMarkdown(server: *Server, arena: std.mem.Allocator, id: std.json.Value,
 }
 
 fn handleLinks(server: *Server, arena: std.mem.Allocator, id: std.json.Value, arguments: ?std.json.Value) !void {
-    const args = parseArgsOrDefault(UrlParams, arena, arguments);
+    const args = try parseArgsOrDefault(UrlParams, arena, arguments, server, id);
     const page = try ensurePage(server, id, args.url);
 
     const content = [_]protocol.TextContent(ToolStreamingText){.{
@@ -350,7 +350,7 @@ fn handleSemanticTree(server: *Server, arena: std.mem.Allocator, id: std.json.Va
         backendNodeId: ?u32 = null,
         maxDepth: ?u32 = null,
     };
-    const args = parseArgsOrDefault(TreeParams, arena, arguments);
+    const args = try parseArgsOrDefault(TreeParams, arena, arguments, server, id);
     const page = try ensurePage(server, id, args.url);
 
     const content = [_]protocol.TextContent(ToolStreamingText){.{
@@ -367,7 +367,7 @@ fn handleSemanticTree(server: *Server, arena: std.mem.Allocator, id: std.json.Va
 }
 
 fn handleInteractiveElements(server: *Server, arena: std.mem.Allocator, id: std.json.Value, arguments: ?std.json.Value) !void {
-    const args = parseArgsOrDefault(UrlParams, arena, arguments);
+    const args = try parseArgsOrDefault(UrlParams, arena, arguments, server, id);
     const page = try ensurePage(server, id, args.url);
 
     const elements = lp.interactive.collectInteractiveElements(page.document.asNode(), arena, page) catch |err| {
@@ -388,7 +388,7 @@ fn handleInteractiveElements(server: *Server, arena: std.mem.Allocator, id: std.
 }
 
 fn handleStructuredData(server: *Server, arena: std.mem.Allocator, id: std.json.Value, arguments: ?std.json.Value) !void {
-    const args = parseArgsOrDefault(UrlParams, arena, arguments);
+    const args = try parseArgsOrDefault(UrlParams, arena, arguments, server, id);
     const page = try ensurePage(server, id, args.url);
 
     const data = lp.structured_data.collectStructuredData(page.document.asNode(), arena, page) catch |err| {
@@ -403,7 +403,7 @@ fn handleStructuredData(server: *Server, arena: std.mem.Allocator, id: std.json.
 }
 
 fn handleDetectForms(server: *Server, arena: std.mem.Allocator, id: std.json.Value, arguments: ?std.json.Value) !void {
-    const args = parseArgsOrDefault(UrlParams, arena, arguments);
+    const args = try parseArgsOrDefault(UrlParams, arena, arguments, server, id);
     const page = try ensurePage(server, id, args.url);
 
     const forms_data = lp.forms.collectForms(arena, page.document.asNode(), page) catch |err| {
@@ -592,13 +592,15 @@ fn ensurePage(server: *Server, id: std.json.Value, url: ?[:0]const u8) !*lp.Page
 }
 
 /// Parses JSON arguments into a given struct type `T`.
-/// If the arguments are missing or invalid, it returns a default-initialized `T` (e.g., `.{}`).
-/// Use this for tools where all arguments are optional and validation failures should be silently ignored.
-fn parseArgsOrDefault(comptime T: type, arena: std.mem.Allocator, arguments: ?std.json.Value) T {
-    if (arguments) |args_raw| {
-        return std.json.parseFromValueLeaky(T, arena, args_raw, .{ .ignore_unknown_fields = true }) catch .{};
-    }
-    return .{};
+/// If the arguments are missing, it returns a default-initialized `T` (e.g., `.{}`).
+/// If the arguments are present but invalid, it sends an MCP error response and returns `error.InvalidParams`.
+/// Use this for tools where all arguments are optional.
+fn parseArgsOrDefault(comptime T: type, arena: std.mem.Allocator, arguments: ?std.json.Value, server: *Server, id: std.json.Value) !T {
+    const args_raw = arguments orelse return .{};
+    return std.json.parseFromValueLeaky(T, arena, args_raw, .{ .ignore_unknown_fields = true }) catch {
+        try server.sendError(id, .InvalidParams, "Invalid arguments");
+        return error.InvalidParams;
+    };
 }
 
 /// Parses JSON arguments into a given struct type `T`.
@@ -606,11 +608,11 @@ fn parseArgsOrDefault(comptime T: type, arena: std.mem.Allocator, arguments: ?st
 /// and returns an `error.InvalidParams`.
 /// Use this for tools that require strict validation or mandatory arguments.
 fn parseArgs(comptime T: type, arena: std.mem.Allocator, arguments: ?std.json.Value, server: *Server, id: std.json.Value, tool_name: []const u8) !T {
-    if (arguments == null) {
+    const args_raw = arguments orelse {
         try server.sendError(id, .InvalidParams, "Missing arguments");
         return error.InvalidParams;
-    }
-    return std.json.parseFromValueLeaky(T, arena, arguments.?, .{ .ignore_unknown_fields = true }) catch {
+    };
+    return std.json.parseFromValueLeaky(T, arena, args_raw, .{ .ignore_unknown_fields = true }) catch {
         const msg = std.fmt.allocPrint(arena, "Invalid arguments for {s}", .{tool_name}) catch "Invalid arguments";
         try server.sendError(id, .InvalidParams, msg);
         return error.InvalidParams;