diff --git a/src/renderer/src/aiCore/prepareParams/parameterBuilder.ts b/src/renderer/src/aiCore/prepareParams/parameterBuilder.ts
index 1d92660072..21b07af811 100644
--- a/src/renderer/src/aiCore/prepareParams/parameterBuilder.ts
+++ b/src/renderer/src/aiCore/prepareParams/parameterBuilder.ts
@@ -26,7 +26,7 @@ import {
   isSupportedThinkingTokenModel,
   isWebSearchModel
 } from '@renderer/config/models'
-import { getHubModeSystemPrompt } from '@renderer/config/prompts'
+import { getAutoModeSystemPrompt } from '@renderer/config/prompts'
 import { fetchAllActiveServerTools } from '@renderer/services/ApiService'
 import { getDefaultModel } from '@renderer/services/AssistantService'
 import store from '@renderer/store'
@@ -245,16 +245,18 @@ export async function buildStreamTextParams(
     params.tools = tools
   }
 
-  if (assistant.prompt) {
-    let systemPrompt = await replacePromptVariables(assistant.prompt, model.name)
-    if (getEffectiveMcpMode(assistant) === 'auto') {
-      const allActiveTools = await fetchAllActiveServerTools()
-      systemPrompt = systemPrompt + '\n\n' + getHubModeSystemPrompt(allActiveTools)
-    }
-    params.system = systemPrompt
-  } else if (getEffectiveMcpMode(assistant) === 'auto') {
+  let systemPrompt = assistant.prompt ? await replacePromptVariables(assistant.prompt, model.name) : ''
+
+  if (getEffectiveMcpMode(assistant) === 'auto') {
     const allActiveTools = await fetchAllActiveServerTools()
-    params.system = getHubModeSystemPrompt(allActiveTools)
+    const autoModePrompt = getAutoModeSystemPrompt(allActiveTools)
+    if (autoModePrompt) {
+      systemPrompt = systemPrompt ? `${systemPrompt}\n\n${autoModePrompt}` : autoModePrompt
+    }
+  }
+
+  if (systemPrompt) {
+    params.system = systemPrompt
   }
 
   logger.debug('params', params)
diff --git a/src/renderer/src/config/prompts.ts b/src/renderer/src/config/prompts.ts
index fda3ec085d..db0128633d 100644
--- a/src/renderer/src/config/prompts.ts
+++ b/src/renderer/src/config/prompts.ts
@@ -619,3 +619,108 @@ export function getHubModeSystemPrompt(tools: ToolInfo[] = []): string {
 ${toolsSection}
 `
 }
+
+const AUTO_MODE_SYSTEM_PROMPT_BASE = `
+You can discover and invoke MCP tools through a hub using TWO meta-tools: \`search\` and \`exec\`.
+
+## Tool Invocation Format
+
+When you want to call a tool, output exactly one XML block:
+
+<tool_use>
+  <name>{tool_name}</name>
+  <arguments>{json_arguments}</arguments>
+</tool_use>
+
+Rules:
+- \`{tool_name}\` MUST be either \`search\` or \`exec\`
+- \`<arguments>\` MUST contain valid JSON (no comments, no trailing commas)
+- Do NOT include extra text before or after the \`<tool_use>\` block
+
+## Available Tools
+
+1. **search** - Discover MCP tools by keyword
+   \`\`\`json
+   { "query": "keyword1,keyword2", "limit": 10 }
+   \`\`\`
+   Returns JavaScript function declarations with JSDoc showing names, parameters, and return types.
+
+2. **exec** - Execute JavaScript that calls discovered tools
+   \`\`\`json
+   { "code": "const r = await ToolName({...}); return r;" }
+   \`\`\`
+   **CRITICAL:** You MUST \`return\` the final value, or result will be \`undefined\`.
+
+## Workflow
+
+1. Call \`search\` with keywords to discover tools
+2. Read the returned function signatures carefully
+3. Call \`exec\` with JavaScript code that:
+   - Uses ONLY functions returned by \`search\`
+   - Calls them with \`await\`
+   - Ends with explicit \`return\`
+4. Answer the user based on the result
+
+## Example
+
+User: "Calculate 15 * 7"
+
+Assistant calls search:
+<tool_use>
+  <name>search</name>
+  <arguments>{"query": "python,calculator"}</arguments>
+</tool_use>
+
+Hub returns function signature:
+\`\`\`js
+async function CherryPython_pythonExecute(params: { code: string }): Promise<unknown>
+\`\`\`
+
+Assistant calls exec:
+<tool_use>
+  <name>exec</name>
+  <arguments>{"code": "const result = await CherryPython_pythonExecute({ code: '15 * 7' }); return result;"}</arguments>
+</tool_use>
+
+Hub returns: { "result": 105 }
+
+Assistant answers: "15 × 7 = 105"
+
+## Common Mistakes
+
+❌ Forgetting to return (result will be undefined):
+\`\`\`js
+await SomeTool({ id: "123" })
+\`\`\`
+
+✅ Always return:
+\`\`\`js
+const data = await SomeTool({ id: "123" }); return data;
+\`\`\`
+
+❌ Calling exec before search - you must discover tools first
+
+❌ Using functions not returned by search
+`
+
+export function getAutoModeSystemPrompt(tools: ToolInfo[] = []): string {
+  if (tools.length === 0) {
+    return ''
+  }
+
+  const existingNames = new Set<string>()
+  const toolsSection = tools
+    .map((t) => {
+      const functionName = generateMcpToolFunctionName(t.serverName, t.name, existingNames)
+      const desc = t.description || ''
+      const normalizedDesc = desc.replace(/\s+/g, ' ').trim()
+      const truncatedDesc = normalizedDesc.length > 50 ? `${normalizedDesc.slice(0, 50)}...` : normalizedDesc
+      return `- ${functionName}: ${truncatedDesc}`
+    })
+    .join('\n')
+
+  return `${AUTO_MODE_SYSTEM_PROMPT_BASE}
+## Discoverable Tools (use search to get full signatures)
+${toolsSection}
+`
+}