fix(outlook): allow clearing message categories by passing an empty array

An explicit empty array now sends categories:[] to clear all labels, a non-empty value replaces, and an absent/empty value leaves them untouched — matching the documented replace semantics.

Author: waleedlatif1

apps/docs/content/docs/en/integrations/outlook.mdx

@@ -337,7 +337,7 @@ Set the categories, follow-up flag, and importance on an Outlook message
 | Parameter | Type | Required | Description |
 | --------- | ---- | -------- | ----------- |
 | `messageId` | string | Yes | The ID of the message to update |
-| `categories` | json | No | Array of category names to assign to the message \(replaces existing categories\) |
+| `categories` | json | No | Array of category names to assign to the message \(replaces existing categories; pass an empty array to clear all\) |
 | `flagStatus` | string | No | Follow-up flag status: notFlagged, flagged, or complete |
 | `importance` | string | No | Message importance: low, normal, or high |
 

apps/sim/tools/outlook/update_message.ts

@@ -66,7 +66,7 @@ export const outlookUpdateMessageTool: ToolConfig<
       required: false,
       visibility: 'user-or-llm',
       description:
-        'Array of category names to assign to the message (replaces existing categories)',
+        'Array of category names to assign to the message (replaces existing categories; pass an empty array to clear all)',
     },
     flagStatus: {
       type: 'string',
@@ -97,9 +97,11 @@ export const outlookUpdateMessageTool: ToolConfig<
     body: (params) => {
       const body: Record<string, unknown> = {}
 
-      const categories = normalizeCategories(params.categories)
-      if (categories.length > 0) {
-        body.categories = categories
+      const rawCategories: unknown = params.categories
+      if (Array.isArray(rawCategories)) {
+        body.categories = normalizeCategories(rawCategories)
+      } else if (typeof rawCategories === 'string' && rawCategories.trim() !== '') {
+        body.categories = normalizeCategories(rawCategories)
       }
 
       if (params.flagStatus) {