diff --git a/packages/core/src/core/__snapshots__/prompts.test.ts.snap b/packages/core/src/core/__snapshots__/prompts.test.ts.snap
index 48afa13515..30603b5443 100644
--- a/packages/core/src/core/__snapshots__/prompts.test.ts.snap
+++ b/packages/core/src/core/__snapshots__/prompts.test.ts.snap
@@ -109,7 +109,7 @@ The following tools are available in Plan Mode:
 ## Rules
 1. **Read-Only:** You cannot modify source code. You may ONLY use read-only tools to explore, and you can only write to \`/tmp/plans/\`. If the user asks you to modify source code directly, you MUST explain that you are in Plan Mode and must first create a plan and get approval.
 2. **Write Constraint:** \`write_file\` and \`replace\` may ONLY be used to write .md plan files to \`/tmp/plans/\`. They cannot modify source code.
-3. **Efficiency:** Autonomously combine discovery and drafting phases to minimize conversational turns. If the request is ambiguous, use \`ask_user\` to clarify.
+3. **Efficiency:** Autonomously combine discovery and drafting phases to minimize conversational turns. If the request is ambiguous, use \`ask_user\` to clarify. Use multi-select to offer flexibility and include detailed descriptions for each option to help the user understand the implications of their choice.
 4. **Inquiries and Directives:** Distinguish between Inquiries and Directives to minimize unnecessary planning.
    - **Inquiries:** If the request is an **Inquiry** (e.g., "How does X work?"), answer directly. DO NOT create a plan.
    - **Directives:** If the request is a **Directive** (e.g., "Fix bug Y"), follow the workflow below.
@@ -277,7 +277,7 @@ The following tools are available in Plan Mode:
 ## Rules
 1. **Read-Only:** You cannot modify source code. You may ONLY use read-only tools to explore, and you can only write to \`/tmp/plans/\`. If the user asks you to modify source code directly, you MUST explain that you are in Plan Mode and must first create a plan and get approval.
 2. **Write Constraint:** \`write_file\` and \`replace\` may ONLY be used to write .md plan files to \`/tmp/plans/\`. They cannot modify source code.
-3. **Efficiency:** Autonomously combine discovery and drafting phases to minimize conversational turns. If the request is ambiguous, use \`ask_user\` to clarify.
+3. **Efficiency:** Autonomously combine discovery and drafting phases to minimize conversational turns. If the request is ambiguous, use \`ask_user\` to clarify. Use multi-select to offer flexibility and include detailed descriptions for each option to help the user understand the implications of their choice.
 4. **Inquiries and Directives:** Distinguish between Inquiries and Directives to minimize unnecessary planning.
    - **Inquiries:** If the request is an **Inquiry** (e.g., "How does X work?"), answer directly. DO NOT create a plan.
    - **Directives:** If the request is a **Directive** (e.g., "Fix bug Y"), follow the workflow below.
@@ -564,7 +564,7 @@ The following tools are available in Plan Mode:
 ## Rules
 1. **Read-Only:** You cannot modify source code. You may ONLY use read-only tools to explore, and you can only write to \`/tmp/project-temp/plans/\`. If the user asks you to modify source code directly, you MUST explain that you are in Plan Mode and must first create a plan and get approval.
 2. **Write Constraint:** \`write_file\` and \`replace\` may ONLY be used to write .md plan files to \`/tmp/project-temp/plans/\`. They cannot modify source code.
-3. **Efficiency:** Autonomously combine discovery and drafting phases to minimize conversational turns. If the request is ambiguous, use \`ask_user\` to clarify.
+3. **Efficiency:** Autonomously combine discovery and drafting phases to minimize conversational turns. If the request is ambiguous, use \`ask_user\` to clarify. Use multi-select to offer flexibility and include detailed descriptions for each option to help the user understand the implications of their choice.
 4. **Inquiries and Directives:** Distinguish between Inquiries and Directives to minimize unnecessary planning.
    - **Inquiries:** If the request is an **Inquiry** (e.g., "How does X work?"), answer directly. DO NOT create a plan.
    - **Directives:** If the request is a **Directive** (e.g., "Fix bug Y"), follow the workflow below.
diff --git a/packages/core/src/prompts/snippets.ts b/packages/core/src/prompts/snippets.ts
index 7f6c5c633e..982a366c3b 100644
--- a/packages/core/src/prompts/snippets.ts
+++ b/packages/core/src/prompts/snippets.ts
@@ -472,7 +472,7 @@ ${options.planModeToolsList}
 ## Rules
 1. **Read-Only:** You cannot modify source code. You may ONLY use read-only tools to explore, and you can only write to \`${options.plansDir}/\`. If the user asks you to modify source code directly, you MUST explain that you are in Plan Mode and must first create a plan and get approval.
 2. **Write Constraint:** ${formatToolName(WRITE_FILE_TOOL_NAME)} and ${formatToolName(EDIT_TOOL_NAME)} may ONLY be used to write .md plan files to \`${options.plansDir}/\`. They cannot modify source code.
-3. **Efficiency:** Autonomously combine discovery and drafting phases to minimize conversational turns. If the request is ambiguous, use ${formatToolName(ASK_USER_TOOL_NAME)} to clarify.
+3. **Efficiency:** Autonomously combine discovery and drafting phases to minimize conversational turns. If the request is ambiguous, use ${formatToolName(ASK_USER_TOOL_NAME)} to clarify. Use multi-select to offer flexibility and include detailed descriptions for each option to help the user understand the implications of their choice.
 4. **Inquiries and Directives:** Distinguish between Inquiries and Directives to minimize unnecessary planning.
    - **Inquiries:** If the request is an **Inquiry** (e.g., "How does X work?"), answer directly. DO NOT create a plan.
    - **Directives:** If the request is a **Directive** (e.g., "Fix bug Y"), follow the workflow below.
diff --git a/packages/core/src/tools/definitions/__snapshots__/coreToolsModelSnapshots.test.ts.snap b/packages/core/src/tools/definitions/__snapshots__/coreToolsModelSnapshots.test.ts.snap
index 2d5cfe8d52..70cf828d86 100644
--- a/packages/core/src/tools/definitions/__snapshots__/coreToolsModelSnapshots.test.ts.snap
+++ b/packages/core/src/tools/definitions/__snapshots__/coreToolsModelSnapshots.test.ts.snap
@@ -859,7 +859,7 @@ exports[`coreTools snapshots for specific models > Model: gemini-3-pro-preview >
 
 exports[`coreTools snapshots for specific models > Model: gemini-3-pro-preview > snapshot for tool: ask_user 1`] = `
 {
-  "description": "Ask the user one or more questions to gather preferences, clarify requirements, or make decisions.",
+  "description": "Ask the user one or more questions to gather preferences, clarify requirements, or make decisions. When using this tool, prefer providing multiple-choice options with detailed descriptions and enable multi-select where appropriate to provide maximum flexibility.",
   "name": "ask_user",
   "parametersJsonSchema": {
     "properties": {
diff --git a/packages/core/src/tools/definitions/model-family-sets/gemini-3.ts b/packages/core/src/tools/definitions/model-family-sets/gemini-3.ts
index 1d50eae7e8..7c4fddc9f6 100644
--- a/packages/core/src/tools/definitions/model-family-sets/gemini-3.ts
+++ b/packages/core/src/tools/definitions/model-family-sets/gemini-3.ts
@@ -558,7 +558,7 @@ The agent did not use the todo list because this task could be completed by a ti
   ask_user: {
     name: ASK_USER_TOOL_NAME,
     description:
-      'Ask the user one or more questions to gather preferences, clarify requirements, or make decisions.',
+      'Ask the user one or more questions to gather preferences, clarify requirements, or make decisions. When using this tool, prefer providing multiple-choice options with detailed descriptions and enable multi-select where appropriate to provide maximum flexibility.',
     parametersJsonSchema: {
       type: 'object',
       required: ['questions'],