diff --git a/h2o-algos/src/main/java/water/tools/MojoConvertTool.java b/h2o-algos/src/main/java/water/tools/MojoConvertTool.java
index 9abd23123068..595f7d964cce 100644
--- a/h2o-algos/src/main/java/water/tools/MojoConvertTool.java
+++ b/h2o-algos/src/main/java/water/tools/MojoConvertTool.java
@@ -33,25 +33,28 @@ void convert() throws IOException {
         Files.write(pojoPath, pojo.getBytes(StandardCharsets.UTF_8));
     }
 
-    private static void usage() {
-        System.err.println("java -cp h2o.jar " + MojoConvertTool.class.getName() + " source_mojo.zip target_pojo.java");
+    public static void main(String[] args) throws IOException {
+        try {
+            mainInternal(args);
+        }
+        catch (IllegalArgumentException e) {
+            System.err.println(e.getMessage());
+            System.exit(1);
+        }
     }
 
-    public static void main(String[] args) throws IOException {
+    public static void mainInternal(String[] args) throws IOException {
         if (args.length < 2) {
-            usage();
-            System.exit(1);
+            throw new IllegalArgumentException("java -cp h2o.jar " + MojoConvertTool.class.getName() + " source_mojo.zip target_pojo.java");
         }
 
         File mojoFile = new File(args[0]);
         if (!mojoFile.isFile()) {
-            System.err.println("Specified MOJO file (" + mojoFile.getAbsolutePath() + ") doesn't exist!");
-            System.exit(2);
+            throw new IllegalArgumentException("Specified MOJO file (" + mojoFile.getAbsolutePath() + ") doesn't exist!");
         }
         File pojoFile = new File(args[1]);
         if (pojoFile.isDirectory() || (pojoFile.getParentFile() != null && !pojoFile.getParentFile().isDirectory())) {
-            System.err.println("Invalid target POJO file (" + pojoFile.getAbsolutePath() + ")! Please specify a file in an existing directory.");
-            System.exit(3);
+            throw new IllegalArgumentException("Invalid target POJO file (" + pojoFile.getAbsolutePath() + ")! Please specify a file in an existing directory.");
         }
 
         System.out.println();
diff --git a/h2o-core/src/main/java/water/rapids/ast/prims/internal/AstRunTool.java b/h2o-core/src/main/java/water/rapids/ast/prims/internal/AstRunTool.java
index 3fe4bf179866..3546ffcd545a 100644
--- a/h2o-core/src/main/java/water/rapids/ast/prims/internal/AstRunTool.java
+++ b/h2o-core/src/main/java/water/rapids/ast/prims/internal/AstRunTool.java
@@ -33,7 +33,7 @@ public ValStr apply(Env env, Env.StackHelp stk, AstRoot[] asts) {
         try {
             // only allow to run approved tools (from our package), not just anything on classpath
             Class<?> clazz = Class.forName(TOOLS_PACKAGE + toolClassName);
-            Method mainMethod = clazz.getDeclaredMethod("main", String[].class);
+            Method mainMethod = clazz.getDeclaredMethod("mainInternal", String[].class);
             mainMethod.invoke(null, new Object[]{args});
         } catch (Exception e) {
             throw new RuntimeException(e);
diff --git a/h2o-extensions/xgboost/src/main/java/water/tools/XGBoostLibExtractTool.java b/h2o-extensions/xgboost/src/main/java/water/tools/XGBoostLibExtractTool.java
index dc94b1835e01..241ea7a93076 100644
--- a/h2o-extensions/xgboost/src/main/java/water/tools/XGBoostLibExtractTool.java
+++ b/h2o-extensions/xgboost/src/main/java/water/tools/XGBoostLibExtractTool.java
@@ -10,19 +10,25 @@
 public class XGBoostLibExtractTool {
 
     public static void main(String[] args) throws IOException {
+        try {
+            mainInternal(args);
+        } catch (IllegalArgumentException e) {
+            System.err.println((e.getMessage());
+            System.exit(1);
+        }
+    }
+
+    public static void mainInternal(String[] args) throws IOException {
         if (args.length != 1) {
-            System.err.println("XGBoostLibExtractTool: Specify target directory where to extract XGBoost native libraries.");
-            System.exit(-1);
+            throw new IllegalArgumentException("XGBoostLibExtractTool: Specify target directory where to extract XGBoost native libraries.");
         }
         File dir = new File(args[0]);
         if (!dir.exists()) {
-            System.err.println("XGBoostLibExtractTool: Directory '" + dir.getAbsolutePath() + "' doesn't exist.");
-            System.exit(-1);
+            throw new IllegalArgumentException("XGBoostLibExtractTool: Directory '" + dir.getAbsolutePath() + "' doesn't exist.");
         }
         NativeLibraryLoaderChain loader = XGBoostExtension.getLoader();
         if (loader == null) {
-            System.err.println("XGBoostLibExtractTool: Failed to locate native libraries.");
-            System.exit(-1);
+            throw new IllegalArgumentException("XGBoostLibExtractTool: Failed to locate native libraries.");
         }
         for (NativeLibrary lib : loader.getNativeLibs()) {
             if (!lib.isBundled())