docs: add conversations_unreads and conversations_mark to README

Author: saoudrizwan

README.md

@@ -13,6 +13,7 @@ This feature-rich Slack MCP Server has:
 - **Enterprise Workspaces Support**: Possibility to integrate with Enterprise Slack setups.
 - **Channel and Thread Support with `#Name` `@Lookup`**: Fetch messages from channels and threads, including activity messages, and retrieve channels using their names (e.g., #general) as well as their IDs.
 - **Smart History**: Fetch messages with pagination by date (d1, 7d, 1m) or message count.
+- **Unread Messages**: Get all unread messages across channels efficiently with priority sorting (DMs > partner channels > internal), @mention filtering, and mark-as-read support.
 - **Search Messages**: Search messages in channels, threads, and DMs using various filters like date, user, and content.
 - **Safe Message Posting**: The `conversations_add_message` tool is disabled by default for safety. Enable it via an environment variable, with optional channel restrictions.
 - **DM and Group DM support**: Retrieve direct messages and group direct messages.
@@ -84,6 +85,21 @@ Get list of channels
   - `limit` (number, default: 100): The maximum number of items to return. Must be an integer between 1 and 1000 (maximum 999).
   - `cursor` (string, optional): Cursor for pagination. Use the value of the last row and column in the response as next_cursor field returned from the previous request.
 
+### 6. conversations_unreads
+Get unread messages across all channels efficiently. Uses a single API call to identify channels with unreads, then fetches only those messages. Results are prioritized: DMs > partner channels (Slack Connect) > internal channels.
+- **Parameters:**
+  - `include_messages` (boolean, default: true): If true, returns the actual unread messages. If false, returns only a summary of channels with unreads.
+  - `channel_types` (string, default: "all"): Filter by channel type: `all`, `dm` (direct messages), `group_dm` (group DMs), `partner` (externally shared channels), `internal` (regular workspace channels).
+  - `max_channels` (number, default: 50): Maximum number of channels to fetch unreads from.
+  - `max_messages_per_channel` (number, default: 10): Maximum messages to fetch per channel.
+  - `mentions_only` (boolean, default: false): If true, only returns channels where you have @mentions.
+
+### 7. conversations_mark
+Mark a channel or DM as read.
+- **Parameters:**
+  - `channel_id` (string, required): ID of the channel in format `Cxxxxxxxxxx` or its name starting with `#...` or `@...` (e.g., `#general`, `@username`).
+  - `ts` (string, optional): Timestamp of the message to mark as read up to. If not provided, marks all messages as read.
+
 ## Resources
 
 The Slack MCP Server exposes two special directory resources for easy access to workspace metadata: