docs(plan): add ask_user tool documentation (#18830)

docs/cli/plan-mode.md

@@ -68,7 +68,7 @@ You can enter Plan Mode in three ways:
 
 ### The Planning Workflow
 
-1.  **Requirements:** The agent clarifies goals using `ask_user`.
+1.  **Requirements:** The agent clarifies goals using [`ask_user`].
 2.  **Exploration:** The agent uses read-only tools (like [`read_file`]) to map
     the codebase and validate assumptions.
 3.  **Design:** The agent proposes alternative approaches with a recommended
@@ -95,7 +95,7 @@ These are the only allowed tools:
 
 - **FileSystem (Read):** [`read_file`], [`list_directory`], [`glob`]
 - **Search:** [`grep_search`], [`google_web_search`]
-- **Interaction:** `ask_user`
+- **Interaction:** [`ask_user`]
 - **MCP Tools (Read):** Read-only [MCP tools] (e.g., `github_read_issue`,
   `postgres_read_schema`) are allowed.
 - **Planning (Write):** [`write_file`] and [`replace`] ONLY allowed for `.md`
@@ -183,3 +183,4 @@ Guide].
 [Policy Engine Guide]: /docs/core/policy-engine.md
 [`enter_plan_mode`]: /docs/tools/planning.md#1-enter_plan_mode-enterplanmode
 [`exit_plan_mode`]: /docs/tools/planning.md#2-exit_plan_mode-exitplanmode
+[`ask_user`]: /docs/tools/ask-user.md

docs/tools/ask-user.md

@@ -0,0 +1,95 @@
+# Ask User Tool
+
+The `ask_user` tool allows the agent to ask you one or more questions to gather
+preferences, clarify requirements, or make decisions. It supports multiple
+question types including multiple-choice, free-form text, and Yes/No
+confirmation.
+
+## `ask_user` (Ask User)
+
+- **Tool name:** `ask_user`
+- **Display name:** Ask User
+- **File:** `ask-user.ts`
+- **Parameters:**
+  - `questions` (array of objects, required): A list of 1 to 4 questions to ask.
+    Each question object has the following properties:
+    - `question` (string, required): The complete question text.
+    - `header` (string, required): A short label (max 16 chars) displayed as a
+      chip/tag (e.g., "Auth", "Database").
+    - `type` (string, optional): The type of question. Defaults to `'choice'`.
+      - `'choice'`: Multiple-choice with options (supports multi-select).
+      - `'text'`: Free-form text input.
+      - `'yesno'`: Yes/No confirmation.
+    - `options` (array of objects, optional): Required for `'choice'` type. 2-4
+      selectable options.
+      - `label` (string, required): Display text (1-5 words).
+      - `description` (string, required): Brief explanation.
+    - `multiSelect` (boolean, optional): For `'choice'` type, allows selecting
+      multiple options.
+    - `placeholder` (string, optional): Hint text for input fields.
+
+- **Behavior:**
+  - Presents an interactive dialog to the user with the specified questions.
+  - Pauses execution until the user provides answers or dismisses the dialog.
+  - Returns the user's answers to the model.
+
+- **Output (`llmContent`):** A JSON string containing the user's answers,
+  indexed by question position (e.g.,
+  `{"answers":{"0": "Option A", "1": "Some text"}}`).
+
+- **Confirmation:** Yes. The tool inherently involves user interaction.
+
+## Usage Examples
+
+### Multiple Choice Question
+
+```json
+{
+  "questions": [
+    {
+      "header": "Database",
+      "question": "Which database would you like to use?",
+      "type": "choice",
+      "options": [
+        {
+          "label": "PostgreSQL",
+          "description": "Powerful, open source object-relational database system."
+        },
+        {
+          "label": "SQLite",
+          "description": "C-library that implements a SQL database engine."
+        }
+      ]
+    }
+  ]
+}
+```
+
+### Text Input Question
+
+```json
+{
+  "questions": [
+    {
+      "header": "Project Name",
+      "question": "What is the name of your new project?",
+      "type": "text",
+      "placeholder": "e.g., my-awesome-app"
+    }
+  ]
+}
+```
+
+### Yes/No Question
+
+```json
+{
+  "questions": [
+    {
+      "header": "Deploy",
+      "question": "Do you want to deploy the application now?",
+      "type": "yesno"
+    }
+  ]
+}
+```

docs/tools/index.md

@@ -87,6 +87,8 @@ Gemini CLI's built-in tools can be broadly categorized as follows:
 - **[Todo Tool](./todos.md) (`write_todos`):** For managing subtasks of complex
   requests.
 - **[Planning Tools](./planning.md):** For entering and exiting Plan Mode.
+- **[Ask User Tool](./ask-user.md) (`ask_user`):** For gathering user input and
+  making decisions.
 
 Additionally, these tools incorporate: