fix(outlook): use consistent set/replace semantics for message categories

Categories are replaced with the provided non-empty list and left unchanged when empty, consistent across the block and agent paths. Drops the ambiguous empty-array clear (clearing all categories isn't expressible unambiguously from the comma-separated field) and updates the description to match.

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 \(replaces existing categories; pass an empty array to clear all\) |
+| `categories` | json | No | Array of category names to assign to the message \(replaces existing categories; leave empty to keep them unchanged\) |
 | `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; pass an empty array to clear all)',
+        'Array of category names to assign to the message (replaces existing categories; leave empty to keep them unchanged)',
     },
     flagStatus: {
       type: 'string',
@@ -97,14 +97,9 @@ export const outlookUpdateMessageTool: ToolConfig<
     body: (params) => {
       const body: Record<string, unknown> = {}
 
-      const rawCategories: unknown = params.categories
-      if (Array.isArray(rawCategories)) {
-        body.categories = normalizeCategories(rawCategories)
-      } else if (typeof rawCategories === 'string') {
-        const normalizedCategories = normalizeCategories(rawCategories)
-        if (normalizedCategories.length > 0) {
-          body.categories = normalizedCategories
-        }
+      const normalizedCategories = normalizeCategories(params.categories)
+      if (normalizedCategories.length > 0) {
+        body.categories = normalizedCategories
       }
 
       if (params.flagStatus) {