diff --git a/packages/cli/src/nonInteractiveCli.test.ts b/packages/cli/src/nonInteractiveCli.test.ts
index a0fc6f9f..938eb4e7 100644
--- a/packages/cli/src/nonInteractiveCli.test.ts
+++ b/packages/cli/src/nonInteractiveCli.test.ts
@@ -8,6 +8,7 @@ import {
   Config,
   executeToolCall,
   ToolRegistry,
+  ToolErrorType,
   shutdownTelemetry,
   GeminiEventType,
   ServerGeminiStreamEvent,
@@ -161,6 +162,7 @@ describe('runNonInteractive', () => {
     };
     mockCoreExecuteToolCall.mockResolvedValue({
       error: new Error('Tool execution failed badly'),
+      errorType: ToolErrorType.UNHANDLED_EXCEPTION,
     });
     mockGeminiClient.sendMessageStream.mockReturnValue(
       createStreamFromEvents([toolCallEvent]),
diff --git a/packages/cli/src/nonInteractiveCli.ts b/packages/cli/src/nonInteractiveCli.ts
index 1d0a7f3d..8e573134 100644
--- a/packages/cli/src/nonInteractiveCli.ts
+++ b/packages/cli/src/nonInteractiveCli.ts
@@ -12,6 +12,7 @@ import {
   shutdownTelemetry,
   isTelemetrySdkInitialized,
   GeminiEventType,
+  ToolErrorType,
 } from '@google/gemini-cli-core';
 import { Content, Part, FunctionCall } from '@google/genai';
 
@@ -97,15 +98,11 @@ export async function runNonInteractive(
           );
 
           if (toolResponse.error) {
-            const isToolNotFound = toolResponse.error.message.includes(
-              'not found in registry',
-            );
             console.error(
               `Error executing tool ${fc.name}: ${toolResponse.resultDisplay || toolResponse.error.message}`,
             );
-            if (!isToolNotFound) {
+            if (toolResponse.errorType === ToolErrorType.UNHANDLED_EXCEPTION)
               process.exit(1);
-            }
           }
 
           if (toolResponse.responseParts) {
diff --git a/packages/core/src/core/coreToolScheduler.ts b/packages/core/src/core/coreToolScheduler.ts
index af078faa..b4c10a64 100644
--- a/packages/core/src/core/coreToolScheduler.ts
+++ b/packages/core/src/core/coreToolScheduler.ts
@@ -19,6 +19,7 @@ import {
   logToolCall,
   ToolCallEvent,
   ToolConfirmationPayload,
+  ToolErrorType,
 } from '../index.js';
 import { Part, PartListUnion } from '@google/genai';
 import { getResponseTextFromParts } from '../utils/generateContentResponseUtilities.js';
@@ -201,6 +202,7 @@ export function convertToFunctionResponse(
 const createErrorResponse = (
   request: ToolCallRequestInfo,
   error: Error,
+  errorType: ToolErrorType | undefined,
 ): ToolCallResponseInfo => ({
   callId: request.callId,
   error,
@@ -212,6 +214,7 @@ const createErrorResponse = (
     },
   },
   resultDisplay: error.message,
+  errorType,
 });
 
 interface CoreToolSchedulerOptions {
@@ -366,6 +369,7 @@ export class CoreToolScheduler {
               },
               resultDisplay,
               error: undefined,
+              errorType: undefined,
             },
             durationMs,
             outcome,
@@ -436,6 +440,7 @@ export class CoreToolScheduler {
             response: createErrorResponse(
               reqInfo,
               new Error(`Tool "${reqInfo.name}" not found in registry.`),
+              ToolErrorType.TOOL_NOT_REGISTERED,
             ),
             durationMs: 0,
           };
@@ -499,6 +504,7 @@ export class CoreToolScheduler {
           createErrorResponse(
             reqInfo,
             error instanceof Error ? error : new Error(String(error)),
+            ToolErrorType.UNHANDLED_EXCEPTION,
           ),
         );
       }
@@ -670,19 +676,30 @@ export class CoreToolScheduler {
               return;
             }
 
-            const response = convertToFunctionResponse(
-              toolName,
-              callId,
-              toolResult.llmContent,
-            );
-            const successResponse: ToolCallResponseInfo = {
-              callId,
-              responseParts: response,
-              resultDisplay: toolResult.returnDisplay,
-              error: undefined,
-            };
-
-            this.setStatusInternal(callId, 'success', successResponse);
+            if (toolResult.error === undefined) {
+              const response = convertToFunctionResponse(
+                toolName,
+                callId,
+                toolResult.llmContent,
+              );
+              const successResponse: ToolCallResponseInfo = {
+                callId,
+                responseParts: response,
+                resultDisplay: toolResult.returnDisplay,
+                error: undefined,
+                errorType: undefined,
+              };
+              this.setStatusInternal(callId, 'success', successResponse);
+            } else {
+              // It is a failure
+              const error = new Error(toolResult.error.message);
+              const errorResponse = createErrorResponse(
+                scheduledCall.request,
+                error,
+                toolResult.error.type,
+              );
+              this.setStatusInternal(callId, 'error', errorResponse);
+            }
           })
           .catch((executionError: Error) => {
             this.setStatusInternal(
@@ -693,6 +710,7 @@ export class CoreToolScheduler {
                 executionError instanceof Error
                   ? executionError
                   : new Error(String(executionError)),
+                ToolErrorType.UNHANDLED_EXCEPTION,
               ),
             );
           });
diff --git a/packages/core/src/core/nonInteractiveToolExecutor.ts b/packages/core/src/core/nonInteractiveToolExecutor.ts
index ab001bd6..52704bf1 100644
--- a/packages/core/src/core/nonInteractiveToolExecutor.ts
+++ b/packages/core/src/core/nonInteractiveToolExecutor.ts
@@ -8,6 +8,7 @@ import {
   logToolCall,
   ToolCallRequestInfo,
   ToolCallResponseInfo,
+  ToolErrorType,
   ToolRegistry,
   ToolResult,
 } from '../index.js';
@@ -56,6 +57,7 @@ export async function executeToolCall(
       ],
       resultDisplay: error.message,
       error,
+      errorType: ToolErrorType.TOOL_NOT_REGISTERED,
     };
   }
 
@@ -79,7 +81,11 @@ export async function executeToolCall(
       function_name: toolCallRequest.name,
       function_args: toolCallRequest.args,
       duration_ms: durationMs,
-      success: true,
+      success: toolResult.error === undefined,
+      error:
+        toolResult.error === undefined ? undefined : toolResult.error.message,
+      error_type:
+        toolResult.error === undefined ? undefined : toolResult.error.type,
       prompt_id: toolCallRequest.prompt_id,
     });
 
@@ -93,7 +99,12 @@ export async function executeToolCall(
       callId: toolCallRequest.callId,
       responseParts: response,
       resultDisplay: tool_display,
-      error: undefined,
+      error:
+        toolResult.error === undefined
+          ? undefined
+          : new Error(toolResult.error.message),
+      errorType:
+        toolResult.error === undefined ? undefined : toolResult.error.type,
     };
   } catch (e) {
     const error = e instanceof Error ? e : new Error(String(e));
@@ -106,6 +117,7 @@ export async function executeToolCall(
       duration_ms: durationMs,
       success: false,
       error: error.message,
+      error_type: ToolErrorType.UNHANDLED_EXCEPTION,
       prompt_id: toolCallRequest.prompt_id,
     });
     return {
@@ -121,6 +133,7 @@ export async function executeToolCall(
       ],
       resultDisplay: error.message,
       error,
+      errorType: ToolErrorType.UNHANDLED_EXCEPTION,
     };
   }
 }
diff --git a/packages/core/src/core/turn.ts b/packages/core/src/core/turn.ts
index b54b3f82..ee32c309 100644
--- a/packages/core/src/core/turn.ts
+++ b/packages/core/src/core/turn.ts
@@ -16,6 +16,7 @@ import {
   ToolResult,
   ToolResultDisplay,
 } from '../tools/tools.js';
+import { ToolErrorType } from '../tools/tool-error.js';
 import { getResponseText } from '../utils/generateContentResponseUtilities.js';
 import { reportError } from '../utils/errorReporting.js';
 import {
@@ -76,6 +77,7 @@ export interface ToolCallResponseInfo {
   responseParts: PartListUnion;
   resultDisplay: ToolResultDisplay | undefined;
   error: Error | undefined;
+  errorType: ToolErrorType | undefined;
 }
 
 export interface ServerToolCallConfirmationDetails {
diff --git a/packages/core/src/index.ts b/packages/core/src/index.ts
index 93862c12..d7dfd90f 100644
--- a/packages/core/src/index.ts
+++ b/packages/core/src/index.ts
@@ -56,6 +56,7 @@ export * from './services/shellExecutionService.js';
 
 // Export base tool definitions
 export * from './tools/tools.js';
+export * from './tools/tool-error.js';
 export * from './tools/tool-registry.js';
 
 // Export prompt logic
diff --git a/packages/core/src/telemetry/loggers.test.circular.ts b/packages/core/src/telemetry/loggers.test.circular.ts
index 62a61bfd..80444a0d 100644
--- a/packages/core/src/telemetry/loggers.test.circular.ts
+++ b/packages/core/src/telemetry/loggers.test.circular.ts
@@ -53,6 +53,7 @@ describe('Circular Reference Handling', () => {
       responseParts: [{ text: 'test result' }],
       resultDisplay: undefined,
       error: undefined, // undefined means success
+      errorType: undefined,
     };
 
     const mockCompletedToolCall: CompletedToolCall = {
@@ -100,6 +101,7 @@ describe('Circular Reference Handling', () => {
       responseParts: [{ text: 'test result' }],
       resultDisplay: undefined,
       error: undefined, // undefined means success
+      errorType: undefined,
     };
 
     const mockCompletedToolCall: CompletedToolCall = {
diff --git a/packages/core/src/telemetry/loggers.test.ts b/packages/core/src/telemetry/loggers.test.ts
index 7a24bcca..3d8116cc 100644
--- a/packages/core/src/telemetry/loggers.test.ts
+++ b/packages/core/src/telemetry/loggers.test.ts
@@ -12,6 +12,7 @@ import {
   ErroredToolCall,
   GeminiClient,
   ToolConfirmationOutcome,
+  ToolErrorType,
   ToolRegistry,
 } from '../index.js';
 import { logs } from '@opentelemetry/api-logs';
@@ -448,6 +449,7 @@ describe('loggers', () => {
           responseParts: 'test-response',
           resultDisplay: undefined,
           error: undefined,
+          errorType: undefined,
         },
         tool: new EditTool(mockConfig),
         durationMs: 100,
@@ -511,6 +513,7 @@ describe('loggers', () => {
           responseParts: 'test-response',
           resultDisplay: undefined,
           error: undefined,
+          errorType: undefined,
         },
         durationMs: 100,
         outcome: ToolConfirmationOutcome.Cancel,
@@ -574,6 +577,7 @@ describe('loggers', () => {
           responseParts: 'test-response',
           resultDisplay: undefined,
           error: undefined,
+          errorType: undefined,
         },
         outcome: ToolConfirmationOutcome.ModifyWithEditor,
         tool: new EditTool(mockConfig),
@@ -638,6 +642,7 @@ describe('loggers', () => {
           responseParts: 'test-response',
           resultDisplay: undefined,
           error: undefined,
+          errorType: undefined,
         },
         tool: new EditTool(mockConfig),
         durationMs: 100,
@@ -703,6 +708,7 @@ describe('loggers', () => {
             name: 'test-error-type',
             message: 'test-error',
           },
+          errorType: ToolErrorType.UNKNOWN,
         },
         durationMs: 100,
       };
@@ -729,8 +735,8 @@ describe('loggers', () => {
           success: false,
           error: 'test-error',
           'error.message': 'test-error',
-          error_type: 'test-error-type',
-          'error.type': 'test-error-type',
+          error_type: ToolErrorType.UNKNOWN,
+          'error.type': ToolErrorType.UNKNOWN,
           prompt_id: 'prompt-id-5',
         },
       });
diff --git a/packages/core/src/telemetry/types.ts b/packages/core/src/telemetry/types.ts
index 1633dbc4..9d1fd77a 100644
--- a/packages/core/src/telemetry/types.ts
+++ b/packages/core/src/telemetry/types.ts
@@ -137,7 +137,7 @@ export class ToolCallEvent {
       ? getDecisionFromOutcome(call.outcome)
       : undefined;
     this.error = call.response.error?.message;
-    this.error_type = call.response.error?.name;
+    this.error_type = call.response.errorType;
     this.prompt_id = call.request.prompt_id;
   }
 }
diff --git a/packages/core/src/telemetry/uiTelemetry.test.ts b/packages/core/src/telemetry/uiTelemetry.test.ts
index 38ba7a91..bce54ad8 100644
--- a/packages/core/src/telemetry/uiTelemetry.test.ts
+++ b/packages/core/src/telemetry/uiTelemetry.test.ts
@@ -22,6 +22,7 @@ import {
   ErroredToolCall,
   SuccessfulToolCall,
 } from '../core/coreToolScheduler.js';
+import { ToolErrorType } from '../tools/tool-error.js';
 import { Tool, ToolConfirmationOutcome } from '../tools/tools.js';
 
 const createFakeCompletedToolCall = (
@@ -54,6 +55,7 @@ const createFakeCompletedToolCall = (
           },
         },
         error: undefined,
+        errorType: undefined,
         resultDisplay: 'Success!',
       },
       durationMs: duration,
@@ -73,6 +75,7 @@ const createFakeCompletedToolCall = (
           },
         },
         error: error || new Error('Tool failed'),
+        errorType: ToolErrorType.UNKNOWN,
         resultDisplay: 'Failure!',
       },
       durationMs: duration,
diff --git a/packages/core/src/tools/edit.test.ts b/packages/core/src/tools/edit.test.ts
index b44d7e6f..029d3a3c 100644
--- a/packages/core/src/tools/edit.test.ts
+++ b/packages/core/src/tools/edit.test.ts
@@ -27,6 +27,7 @@ vi.mock('../utils/editor.js', () => ({
 import { describe, it, expect, beforeEach, afterEach, vi, Mock } from 'vitest';
 import { EditTool, EditToolParams } from './edit.js';
 import { FileDiff } from './tools.js';
+import { ToolErrorType } from './tool-error.js';
 import path from 'path';
 import fs from 'fs';
 import os from 'os';
@@ -627,6 +628,98 @@ describe('EditTool', () => {
     });
   });
 
+  describe('Error Scenarios', () => {
+    const testFile = 'error_test.txt';
+    let filePath: string;
+
+    beforeEach(() => {
+      filePath = path.join(rootDir, testFile);
+    });
+
+    it('should return FILE_NOT_FOUND error', async () => {
+      const params: EditToolParams = {
+        file_path: filePath,
+        old_string: 'any',
+        new_string: 'new',
+      };
+      const result = await tool.execute(params, new AbortController().signal);
+      expect(result.error?.type).toBe(ToolErrorType.FILE_NOT_FOUND);
+    });
+
+    it('should return ATTEMPT_TO_CREATE_EXISTING_FILE error', async () => {
+      fs.writeFileSync(filePath, 'existing content', 'utf8');
+      const params: EditToolParams = {
+        file_path: filePath,
+        old_string: '',
+        new_string: 'new content',
+      };
+      const result = await tool.execute(params, new AbortController().signal);
+      expect(result.error?.type).toBe(
+        ToolErrorType.ATTEMPT_TO_CREATE_EXISTING_FILE,
+      );
+    });
+
+    it('should return NO_OCCURRENCE_FOUND error', async () => {
+      fs.writeFileSync(filePath, 'content', 'utf8');
+      const params: EditToolParams = {
+        file_path: filePath,
+        old_string: 'not-found',
+        new_string: 'new',
+      };
+      const result = await tool.execute(params, new AbortController().signal);
+      expect(result.error?.type).toBe(ToolErrorType.EDIT_NO_OCCURRENCE_FOUND);
+    });
+
+    it('should return EXPECTED_OCCURRENCE_MISMATCH error', async () => {
+      fs.writeFileSync(filePath, 'one one two', 'utf8');
+      const params: EditToolParams = {
+        file_path: filePath,
+        old_string: 'one',
+        new_string: 'new',
+        expected_replacements: 3,
+      };
+      const result = await tool.execute(params, new AbortController().signal);
+      expect(result.error?.type).toBe(
+        ToolErrorType.EDIT_EXPECTED_OCCURRENCE_MISMATCH,
+      );
+    });
+
+    it('should return NO_CHANGE error', async () => {
+      fs.writeFileSync(filePath, 'content', 'utf8');
+      const params: EditToolParams = {
+        file_path: filePath,
+        old_string: 'content',
+        new_string: 'content',
+      };
+      const result = await tool.execute(params, new AbortController().signal);
+      expect(result.error?.type).toBe(ToolErrorType.EDIT_NO_CHANGE);
+    });
+
+    it('should return INVALID_PARAMETERS error for relative path', async () => {
+      const params: EditToolParams = {
+        file_path: 'relative/path.txt',
+        old_string: 'a',
+        new_string: 'b',
+      };
+      const result = await tool.execute(params, new AbortController().signal);
+      expect(result.error?.type).toBe(ToolErrorType.INVALID_TOOL_PARAMS);
+    });
+
+    it('should return FILE_WRITE_FAILURE on write error', async () => {
+      fs.writeFileSync(filePath, 'content', 'utf8');
+      // Make file readonly to trigger a write error
+      fs.chmodSync(filePath, '444');
+
+      const params: EditToolParams = {
+        file_path: filePath,
+        old_string: 'content',
+        new_string: 'new content',
+      };
+      const result = await tool.execute(params, new AbortController().signal);
+      expect(result.error?.type).toBe(ToolErrorType.FILE_WRITE_FAILURE);
+    });
+  });
+
   describe('getDescription', () => {
     it('should return "No file changes to..." if old_string and new_string are the same', () => {
       const testFileName = 'test.txt';
diff --git a/packages/core/src/tools/edit.ts b/packages/core/src/tools/edit.ts
index ff2bc204..25da2292 100644
--- a/packages/core/src/tools/edit.ts
+++ b/packages/core/src/tools/edit.ts
@@ -17,6 +17,7 @@ import {
   ToolResult,
   ToolResultDisplay,
 } from './tools.js';
+import { ToolErrorType } from './tool-error.js';
 import { Type } from '@google/genai';
 import { SchemaValidator } from '../utils/schemaValidator.js';
 import { makeRelative, shortenPath } from '../utils/paths.js';
@@ -62,7 +63,7 @@ interface CalculatedEdit {
   currentContent: string | null;
   newContent: string;
   occurrences: number;
-  error?: { display: string; raw: string };
+  error?: { display: string; raw: string; type: ToolErrorType };
   isNewFile: boolean;
 }
 
@@ -191,7 +192,9 @@ Expectation for required parameters:
     let finalNewString = params.new_string;
     let finalOldString = params.old_string;
     let occurrences = 0;
-    let error: { display: string; raw: string } | undefined = undefined;
+    let error:
+      | { display: string; raw: string; type: ToolErrorType }
+      | undefined = undefined;
 
     try {
       currentContent = fs.readFileSync(params.file_path, 'utf8');
@@ -214,6 +217,7 @@ Expectation for required parameters:
       error = {
         display: `File not found. Cannot apply edit. Use an empty old_string to create a new file.`,
         raw: `File not found: ${params.file_path}`,
+        type: ToolErrorType.FILE_NOT_FOUND,
       };
     } else if (currentContent !== null) {
       // Editing an existing file
@@ -233,11 +237,13 @@ Expectation for required parameters:
         error = {
           display: `Failed to edit. Attempted to create a file that already exists.`,
           raw: `File already exists, cannot create: ${params.file_path}`,
+          type: ToolErrorType.ATTEMPT_TO_CREATE_EXISTING_FILE,
         };
       } else if (occurrences === 0) {
         error = {
           display: `Failed to edit, could not find the string to replace.`,
           raw: `Failed to edit, 0 occurrences found for old_string in ${params.file_path}. No edits made. The exact text in old_string was not found. Ensure you're not escaping content incorrectly and check whitespace, indentation, and context. Use ${ReadFileTool.Name} tool to verify.`,
+          type: ToolErrorType.EDIT_NO_OCCURRENCE_FOUND,
         };
       } else if (occurrences !== expectedReplacements) {
         const occurrenceTerm =
@@ -246,11 +252,13 @@ Expectation for required parameters:
         error = {
           display: `Failed to edit, expected ${expectedReplacements} ${occurrenceTerm} but found ${occurrences}.`,
           raw: `Failed to edit, Expected ${expectedReplacements} ${occurrenceTerm} but found ${occurrences} for old_string in file: ${params.file_path}`,
+          type: ToolErrorType.EDIT_EXPECTED_OCCURRENCE_MISMATCH,
         };
       } else if (finalOldString === finalNewString) {
         error = {
           display: `No changes to apply. The old_string and new_string are identical.`,
           raw: `No changes to apply. The old_string and new_string are identical in file: ${params.file_path}`,
+          type: ToolErrorType.EDIT_NO_CHANGE,
         };
       }
     } else {
@@ -258,6 +266,7 @@ Expectation for required parameters:
       error = {
         display: `Failed to read content of file.`,
         raw: `Failed to read content of existing file: ${params.file_path}`,
+        type: ToolErrorType.READ_CONTENT_FAILURE,
       };
     }
 
@@ -374,6 +383,10 @@ Expectation for required parameters:
       return {
         llmContent: `Error: Invalid parameters provided. Reason: ${validationError}`,
         returnDisplay: `Error: ${validationError}`,
+        error: {
+          message: validationError,
+          type: ToolErrorType.INVALID_TOOL_PARAMS,
+        },
       };
     }
 
@@ -385,6 +398,10 @@ Expectation for required parameters:
       return {
         llmContent: `Error preparing edit: ${errorMsg}`,
         returnDisplay: `Error preparing edit: ${errorMsg}`,
+        error: {
+          message: errorMsg,
+          type: ToolErrorType.EDIT_PREPARATION_FAILURE,
+        },
       };
     }
 
@@ -392,6 +409,10 @@ Expectation for required parameters:
       return {
         llmContent: editData.error.raw,
         returnDisplay: `Error: ${editData.error.display}`,
+        error: {
+          message: editData.error.raw,
+          type: editData.error.type,
+        },
       };
     }
 
@@ -442,6 +463,10 @@ Expectation for required parameters:
       return {
         llmContent: `Error executing edit: ${errorMsg}`,
         returnDisplay: `Error writing file: ${errorMsg}`,
+        error: {
+          message: errorMsg,
+          type: ToolErrorType.FILE_WRITE_FAILURE,
+        },
       };
     }
   }
diff --git a/packages/core/src/tools/tool-error.ts b/packages/core/src/tools/tool-error.ts
new file mode 100644
index 00000000..38caa1da
--- /dev/null
+++ b/packages/core/src/tools/tool-error.ts
@@ -0,0 +1,28 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * A type-safe enum for tool-related errors.
+ */
+export enum ToolErrorType {
+  // General Errors
+  INVALID_TOOL_PARAMS = 'invalid_tool_params',
+  UNKNOWN = 'unknown',
+  UNHANDLED_EXCEPTION = 'unhandled_exception',
+  TOOL_NOT_REGISTERED = 'tool_not_registered',
+
+  // File System Errors
+  FILE_NOT_FOUND = 'file_not_found',
+  FILE_WRITE_FAILURE = 'file_write_failure',
+  READ_CONTENT_FAILURE = 'read_content_failure',
+  ATTEMPT_TO_CREATE_EXISTING_FILE = 'attempt_to_create_existing_file',
+
+  // Edit-specific Errors
+  EDIT_PREPARATION_FAILURE = 'edit_preparation_failure',
+  EDIT_NO_OCCURRENCE_FOUND = 'edit_no_occurrence_found',
+  EDIT_EXPECTED_OCCURRENCE_MISMATCH = 'edit_expected_occurrence_mismatch',
+  EDIT_NO_CHANGE = 'edit_no_change',
+}
diff --git a/packages/core/src/tools/tools.ts b/packages/core/src/tools/tools.ts
index 0d7b402a..0e3ffabf 100644
--- a/packages/core/src/tools/tools.ts
+++ b/packages/core/src/tools/tools.ts
@@ -5,6 +5,7 @@
  */
 
 import { FunctionDeclaration, PartListUnion, Schema } from '@google/genai';
+import { ToolErrorType } from './tool-error.js';
 
 /**
  * Interface representing the base Tool functionality
@@ -217,6 +218,14 @@ export interface ToolResult {
    * For now, we keep it as the core logic in ReadFileTool currently produces it.
    */
   returnDisplay: ToolResultDisplay;
+
+  /**
+   * If this property is present, the tool call is considered a failure.
+   */
+  error?: {
+    message: string; // raw error message
+    type?: ToolErrorType; // An optional machine-readable error type (e.g., 'FILE_NOT_FOUND').
+  };
 }
 
 export type ToolResultDisplay = string | FileDiff;