diff --git a/src/headless.ts b/src/headless.ts
index 6300d4e..8af5bdd 100644
--- a/src/headless.ts
+++ b/src/headless.ts
@@ -41,9 +41,9 @@ import {
 import { SYSTEM_REMINDER_CLOSE, SYSTEM_REMINDER_OPEN } from "./constants";
 import { settingsManager } from "./settings-manager";
 import {
+  type ExternalToolDefinition,
   registerExternalTools,
   setExternalToolExecutor,
-  type ExternalToolDefinition,
 } from "./tools/manager";
 import type {
   AutoApprovalMessage,
@@ -2108,11 +2108,13 @@ async function runBidirectionalMode(
         console.log(JSON.stringify(interruptResponse));
       } else if (subtype === "register_external_tools") {
         // Register external tools from SDK
-        const toolsRequest = message.request as { tools?: ExternalToolDefinition[] };
+        const toolsRequest = message.request as {
+          tools?: ExternalToolDefinition[];
+        };
         const tools = toolsRequest.tools ?? [];
-        
+
         registerExternalTools(tools);
-        
+
         // Set up the external tool executor to send requests back to SDK
         setExternalToolExecutor(async (toolCallId, toolName, input) => {
           // Send execute_external_tool request to SDK
@@ -2127,15 +2129,18 @@ async function runBidirectionalMode(
             } as unknown as CanUseToolControlRequest, // Type cast for compatibility
           };
           console.log(JSON.stringify(execRequest));
-          
+
           // Wait for external_tool_result response
           while (true) {
             const line = await getNextLine();
             if (line === null) {
-              return { content: [{ type: "text", text: "stdin closed" }], isError: true };
+              return {
+                content: [{ type: "text", text: "stdin closed" }],
+                isError: true,
+              };
             }
             if (!line.trim()) continue;
-            
+
             try {
               const msg = JSON.parse(line);
               if (
@@ -2153,7 +2158,7 @@ async function runBidirectionalMode(
             }
           }
         });
-        
+
         const registerResponse: ControlResponse = {
           type: "control_response",
           response: {
diff --git a/src/tools/manager.ts b/src/tools/manager.ts
index 8f0a627..7ea9172 100644
--- a/src/tools/manager.ts
+++ b/src/tools/manager.ts
@@ -382,7 +382,12 @@ export type ExternalToolExecutor = (
   toolName: string,
   input: Record<string, unknown>,
 ) => Promise<{
-  content: Array<{ type: string; text?: string; data?: string; mimeType?: string }>;
+  content: Array<{
+    type: string;
+    text?: string;
+    data?: string;
+    mimeType?: string;
+  }>;
   isError: boolean;
 }>;
 
@@ -438,7 +443,9 @@ export function isExternalTool(name: string): boolean {
 /**
  * Get external tool definition
  */
-export function getExternalToolDefinition(name: string): ExternalToolDefinition | undefined {
+export function getExternalToolDefinition(
+  name: string,
+): ExternalToolDefinition | undefined {
   return getExternalToolsRegistry().get(name);
 }
 
@@ -461,7 +468,9 @@ export async function executeExternalTool(
   toolName: string,
   input: Record<string, unknown>,
 ): Promise<ToolExecutionResult> {
-  const executor = (globalThis as GlobalWithExternalTools)[EXTERNAL_EXECUTOR_KEY];
+  const executor = (globalThis as GlobalWithExternalTools)[
+    EXTERNAL_EXECUTOR_KEY
+  ];
   if (!executor) {
     return {
       toolReturn: `External tool executor not set for tool: ${toolName}`,
@@ -471,13 +480,13 @@ export async function executeExternalTool(
 
   try {
     const result = await executor(toolCallId, toolName, input);
-    
+
     // Convert external tool result to ToolExecutionResult format
     const textContent = result.content
       .filter((c) => c.type === "text" && c.text)
       .map((c) => c.text)
       .join("\n");
-    
+
     return {
       toolReturn: textContent || JSON.stringify(result.content),
       status: result.isError ? "error" : "success",
@@ -498,14 +507,16 @@ export async function executeExternalTool(
  */
 export function getClientToolsFromRegistry(): ClientTool[] {
   // Get built-in tools
-  const builtInTools = Array.from(toolRegistry.entries()).map(([name, tool]) => {
-    const serverName = getServerToolName(name);
-    return {
-      name: serverName,
-      description: tool.schema.description,
-      parameters: tool.schema.input_schema,
-    };
-  });
+  const builtInTools = Array.from(toolRegistry.entries()).map(
+    ([name, tool]) => {
+      const serverName = getServerToolName(name);
+      return {
+        name: serverName,
+        description: tool.schema.description,
+        parameters: tool.schema.input_schema,
+      };
+    },
+  );
 
   // Add external tools
   const externalTools = getExternalToolsAsClientTools();
diff --git a/src/types/protocol.ts b/src/types/protocol.ts
index b217f8b..9015e1f 100644
--- a/src/types/protocol.ts
+++ b/src/types/protocol.ts
@@ -307,8 +307,8 @@ export interface ExecuteExternalToolRequest {
   input: Record<string, unknown>;
 }
 
-export type CliToSdkControlRequest = 
-  | CanUseToolControlRequest 
+export type CliToSdkControlRequest =
+  | CanUseToolControlRequest
   | ExecuteExternalToolRequest;
 
 // Combined for parsing
@@ -357,7 +357,7 @@ export type CanUseToolResponse =
 export interface ExternalToolResultContent {
   type: "text" | "image";
   text?: string;
-  data?: string;      // base64 for images
+  data?: string; // base64 for images
   mimeType?: string;
 }