diff --git a/README.md b/README.md
index 3860ab8..504e0c6 100644
--- a/README.md
+++ b/README.md
@@ -662,9 +662,9 @@ X Y coordinate space, based on the provided screenshot.
 
 - **browser_tab_select**
   - Title: Select a tab
-  - Description: Select a tab by index
+  - Description: Select a tab by index (1-based indexing)
   - Parameters:
-    - `index` (number): The index of the tab to select
+    - `index` (number): The index of the tab to select (1-based: first tab is 1, second tab is 2, etc.)
   - Read-only: **true**
 
 <!-- NOTE: This has been generated via update-readme.js -->
@@ -673,7 +673,7 @@ X Y coordinate space, based on the provided screenshot.
   - Title: Close a tab
   - Description: Close a tab
   - Parameters:
-    - `index` (number, optional): The index of the tab to close. Closes current tab if not provided.
+    - `index` (number, optional): The index of the tab to close (1-based: first tab is 1, second tab is 2, etc.). Closes current tab if not provided.
   - Read-only: **false**
 
 </details>
diff --git a/src/tools/tabs.ts b/src/tools/tabs.ts
index 4133bf1..4484c9d 100644
--- a/src/tools/tabs.ts
+++ b/src/tools/tabs.ts
@@ -50,9 +50,9 @@ const selectTab: ToolFactory = captureSnapshot => defineTool({
   schema: {
     name: 'browser_tab_select',
     title: 'Select a tab',
-    description: 'Select a tab by index',
+    description: 'Select a tab by index (1-based indexing)',
     inputSchema: z.object({
-      index: z.number().describe('The index of the tab to select'),
+      index: z.number().describe('The index of the tab to select (1-based: first tab is 1, second tab is 2, etc.)'),
     }),
     type: 'readOnly',
   },
@@ -108,7 +108,7 @@ const closeTab: ToolFactory = captureSnapshot => defineTool({
     title: 'Close a tab',
     description: 'Close a tab',
     inputSchema: z.object({
-      index: z.number().optional().describe('The index of the tab to close. Closes current tab if not provided.'),
+      index: z.number().optional().describe('The index of the tab to close (1-based: first tab is 1, second tab is 2, etc.). Closes current tab if not provided.'),
     }),
     type: 'destructive',
   },