diff --git a/src/cmdforge/gui/pages/tool_builder_page.py b/src/cmdforge/gui/pages/tool_builder_page.py
index 145ec9c..02f1e04 100644
--- a/src/cmdforge/gui/pages/tool_builder_page.py
+++ b/src/cmdforge/gui/pages/tool_builder_page.py
@@ -133,6 +133,47 @@ class ToolBuilderPage(QWidget):
 
         left_layout.addWidget(args_box)
 
+        # Dependencies group
+        deps_box = QGroupBox()
+        deps_layout = QVBoxLayout(deps_box)
+
+        deps_label = QLabel("Dependencies")
+        deps_label.setObjectName("sectionHeading")
+        deps_label.setToolTip(
+            "<p>Dependencies are other CmdForge tools this tool requires.</p>"
+            "<p>If your code steps call other tools via subprocess,<br>"
+            "declare them here so the dependency system knows about them.</p>"
+            "<p>Use this when you can't use a Tool step directly<br>"
+            "(e.g., calling tools in a loop or with complex logic).</p>"
+        )
+        deps_layout.addWidget(deps_label)
+
+        self.deps_list = QListWidget()
+        self.deps_list.setMaximumHeight(100)
+        deps_layout.addWidget(self.deps_list)
+
+        # Dependency add row: combo + add button
+        deps_add_row = QHBoxLayout()
+        self.deps_combo = QComboBox()
+        self.deps_combo.setEditable(True)
+        self.deps_combo.setPlaceholderText("Select or type tool name...")
+        self.deps_combo.setToolTip("Select an installed tool or type a tool reference (e.g., official/summarize)")
+        self._populate_deps_combo()
+        deps_add_row.addWidget(self.deps_combo, 1)
+
+        self.btn_add_dep = QPushButton("Add")
+        self.btn_add_dep.clicked.connect(self._add_dependency)
+        deps_add_row.addWidget(self.btn_add_dep)
+
+        self.btn_del_dep = QPushButton("Remove")
+        self.btn_del_dep.setObjectName("danger")
+        self.btn_del_dep.clicked.connect(self._delete_dependency)
+        deps_add_row.addWidget(self.btn_del_dep)
+
+        deps_layout.addLayout(deps_add_row)
+
+        left_layout.addWidget(deps_box)
+
         splitter.addWidget(left)
 
         # Right: Steps and output
@@ -406,6 +447,9 @@ class ToolBuilderPage(QWidget):
         # Load arguments
         self._refresh_arguments()
 
+        # Load dependencies
+        self._refresh_dependencies()
+
         # Load steps
         self._refresh_steps()
 
@@ -579,6 +623,66 @@ class ToolBuilderPage(QWidget):
         del self._tool.arguments[idx]
         self._refresh_arguments()
 
+    def _populate_deps_combo(self):
+        """Populate dependencies combo with installed tools."""
+        from ...tool import TOOLS_DIR
+        self.deps_combo.clear()
+
+        # Get all installed tools
+        tools = []
+        if TOOLS_DIR.exists():
+            for item in TOOLS_DIR.iterdir():
+                if item.is_dir():
+                    config = item / "config.yaml"
+                    if config.exists():
+                        tools.append(item.name)
+
+        # Sort and add to combo
+        for tool in sorted(tools):
+            self.deps_combo.addItem(tool)
+
+    def _add_dependency(self):
+        """Add selected tool to dependencies."""
+        tool_ref = self.deps_combo.currentText().strip()
+        if not tool_ref:
+            return
+
+        if not self._tool:
+            # Create a minimal tool object if none exists
+            self._tool = Tool(name="", description="")
+
+        # Initialize dependencies list if needed
+        if not hasattr(self._tool, 'dependencies') or self._tool.dependencies is None:
+            self._tool.dependencies = []
+
+        # Check if already in list
+        if tool_ref in self._tool.dependencies:
+            self.main_window.show_status(f"'{tool_ref}' is already a dependency")
+            return
+
+        self._tool.dependencies.append(tool_ref)
+        self._refresh_dependencies()
+        self.deps_combo.setCurrentText("")
+        self.main_window.show_status(f"Added dependency: {tool_ref}")
+
+    def _delete_dependency(self):
+        """Remove selected dependency."""
+        items = self.deps_list.selectedItems()
+        if not items:
+            return
+
+        dep = items[0].text()
+        if self._tool and self._tool.dependencies and dep in self._tool.dependencies:
+            self._tool.dependencies.remove(dep)
+            self._refresh_dependencies()
+
+    def _refresh_dependencies(self):
+        """Refresh dependencies list widget."""
+        self.deps_list.clear()
+        if self._tool and self._tool.dependencies:
+            for dep in self._tool.dependencies:
+                self.deps_list.addItem(dep)
+
     def _add_tool_dependency(self, tool_ref: str):
         """Add a tool reference to the dependencies list if not already present.
 
@@ -830,13 +934,18 @@ class ToolBuilderPage(QWidget):
             category=category,
             arguments=self._tool.arguments if self._tool else [],
             steps=self._tool.steps if self._tool else [],
-            output=output
+            output=output,
+            dependencies=self._tool.dependencies if self._tool else []
         )
 
         # Preserve source if editing
         if self._tool and self._tool.source:
             tool.source = self._tool.source
 
+        # Preserve version if editing
+        if self._tool and self._tool.version:
+            tool.version = self._tool.version
+
         try:
             save_tool(tool)
             self.main_window.show_status(f"Saved tool '{name}'")