diff --git a/.python-version b/.python-version
index 24ee5b1..7eebfaf 100644
--- a/.python-version
+++ b/.python-version
@@ -1 +1 @@
-3.13
+3.12.11
diff --git a/README.md b/README.md
index 125f847..efca7da 100644
--- a/README.md
+++ b/README.md
@@ -116,6 +116,16 @@ This MCP server exposes a huge suite of Telegram tools. **Every major Telegram/T
 - **unarchive_chat(chat_id)**: Unarchive a chat
 - **get_recent_actions(chat_id)**: Get recent admin actions
 
+### Input Validation
+
+To improve robustness, all functions accepting `chat_id` or `user_id` parameters now include input validation. You can use any of the following formats for these IDs:
+
+-   **Integer ID**: The direct integer ID for a user, chat, or channel (e.g., `123456789` or `-1001234567890`).
+-   **String ID**: The integer ID provided as a string (e.g., `"123456789"`).
+-   **Username**: The public username for a user or channel (e.g., `"@username"` or `"username"`).
+
+The server will automatically validate the input and convert it to the correct format before making a request to Telegram. If the input is invalid, a clear error message will be returned.
+
 ## Removed Functionality
 
 Please note that tools requiring direct file path access on the server (`send_file`, `download_media`, `set_profile_photo`, `edit_chat_photo`, `send_voice`, `send_sticker`, `upload_file`) have been removed from `main.py`. This is due to limitations in the current MCP environment regarding handling file attachments and local file system paths.
diff --git a/main.py b/main.py
index 6fb590e..dc6c49c 100644
--- a/main.py
+++ b/main.py
@@ -30,9 +30,16 @@ from telethon.tl.types import (
     InputPeerChat,
     InputPeerChannel,
 )
+import re
+from functools import wraps
 import telethon.errors.rpcerrorlist
 
 
+class ValidationError(Exception):
+    """Custom exception for validation errors."""
+    pass
+
+
 def json_serializer(obj):
     """Helper function to convert non-serializable objects for JSON serialization."""
     if isinstance(obj, datetime):
@@ -109,7 +116,7 @@ ERROR_PREFIXES = {
 
 
 def log_and_format_error(
-    function_name: str, error: Exception, prefix: str = None, **kwargs
+    function_name: str, error: Exception, prefix: str = None, user_message: str = None, **kwargs
 ) -> str:
     """
     Centralized error handling function that logs the error and returns a formatted user-friendly message.
@@ -118,13 +125,16 @@ def log_and_format_error(
         function_name: Name of the function where error occurred
         error: The exception that was raised
         prefix: Error code prefix (e.g., "CHAT", "MSG") - if None, will be derived from function_name
+        user_message: A custom user-facing message to return. If None, a generic one is created.
         **kwargs: Additional context parameters to include in log
 
     Returns:
         A user-friendly error message with error code
     """
     # Generate a consistent error code
-    if prefix is None:
+    if prefix == "VALIDATION-001":
+        error_code = prefix
+    elif prefix is None:
         # Try to derive prefix from function name
         for key, value in ERROR_PREFIXES.items():
             if key in function_name.lower():
@@ -132,19 +142,93 @@ def log_and_format_error(
                 break
         if prefix is None:
             prefix = "GEN"  # Generic prefix if none matches
+        error_code = f"{prefix}-ERR-{abs(hash(function_name)) % 1000:03d}"
+    else:
+        error_code = f"{prefix}-ERR-{abs(hash(function_name)) % 1000:03d}"
 
-    error_code = f"{prefix}-ERR-{abs(hash(function_name)) % 1000:03d}"
 
     # Format the additional context parameters
     context = ", ".join(f"{k}={v}" for k, v in kwargs.items())
 
     # Log the full technical error
-    logger.exception(f"{function_name} failed ({context}): {error}")
+    logger.error(f"Error in {function_name} ({context}) - Code: {error_code}", exc_info=True)
 
     # Return a user-friendly message
+    if user_message:
+        return user_message
+
     return f"An error occurred (code: {error_code}). Check mcp_errors.log for details."
 
 
+def validate_id(*param_names_to_validate):
+    """
+    Decorator to validate chat_id and user_id parameters, including lists of IDs.
+    It checks for valid integer ranges, string representations of integers,
+    and username formats.
+    """
+    def decorator(func):
+        @wraps(func)
+        async def wrapper(*args, **kwargs):
+            for param_name in param_names_to_validate:
+                if param_name not in kwargs or kwargs[param_name] is None:
+                    continue
+
+                param_value = kwargs[param_name]
+
+                def validate_single_id(value, p_name):
+                    # Handle integer IDs
+                    if isinstance(value, int):
+                        if not (-2**63 <= value <= 2**63 - 1):
+                            return None, f"Invalid {p_name}: {value}. ID is out of the valid integer range."
+                        return value, None
+
+                    # Handle string IDs
+                    if isinstance(value, str):
+                        try:
+                            int_value = int(value)
+                            if not (-2**63 <= int_value <= 2**63 - 1):
+                                return None, f"Invalid {p_name}: {value}. ID is out of the valid integer range."
+                            return int_value, None
+                        except ValueError:
+                            if re.match(r'^@?[a-zA-Z0-9_]{5,}$', value):
+                                return value, None
+                            else:
+                                return None, f"Invalid {p_name}: '{value}'. Must be a valid integer ID, or a username string."
+
+                    # Handle other invalid types
+                    return None, f"Invalid {p_name}: {value}. Type must be an integer or a string."
+
+                if isinstance(param_value, list):
+                    validated_list = []
+                    for item in param_value:
+                        validated_item, error_msg = validate_single_id(item, param_name)
+                        if error_msg:
+                            return log_and_format_error(
+                                func.__name__,
+                                ValidationError(error_msg),
+                                prefix="VALIDATION-001",
+                                user_message=error_msg,
+                                **{param_name: param_value}
+                            )
+                        validated_list.append(validated_item)
+                    kwargs[param_name] = validated_list
+                else:
+                    validated_value, error_msg = validate_single_id(param_value, param_name)
+                    if error_msg:
+                        return log_and_format_error(
+                            func.__name__,
+                            ValidationError(error_msg),
+                            prefix="VALIDATION-001",
+                            user_message=error_msg,
+                            **{param_name: param_value}
+                        )
+                    kwargs[param_name] = validated_value
+
+            return await func(*args, **kwargs)
+        return wrapper
+    return decorator
+
+
 def format_entity(entity) -> Dict[str, Any]:
     """Helper function to format entity information consistently."""
     result = {"id": entity.id}
@@ -231,11 +315,12 @@ async def get_chats(page: int = 1, page_size: int = 20) -> str:
 
 
 @mcp.tool()
-async def get_messages(chat_id: int, page: int = 1, page_size: int = 20) -> str:
+@validate_id('chat_id')
+async def get_messages(chat_id: Union[int, str], page: int = 1, page_size: int = 20) -> str:
     """
     Get paginated messages from a specific chat.
     Args:
-        chat_id: The ID of the chat.
+        chat_id: The ID or username of the chat.
         page: Page number (1-indexed).
         page_size: Number of messages per page.
     """
@@ -262,11 +347,12 @@ async def get_messages(chat_id: int, page: int = 1, page_size: int = 20) -> str:
 
 
 @mcp.tool()
-async def send_message(chat_id: int, message: str) -> str:
+@validate_id('chat_id')
+async def send_message(chat_id: Union[int, str], message: str) -> str:
     """
     Send a message to a specific chat.
     Args:
-        chat_id: The ID of the chat.
+        chat_id: The ID or username of the chat.
         message: The message content to send.
     """
     try:
@@ -346,8 +432,9 @@ async def get_contact_ids() -> str:
 
 
 @mcp.tool()
+@validate_id('chat_id')
 async def list_messages(
-    chat_id: int,
+    chat_id: Union[int, str],
     limit: int = 20,
     search_query: str = None,
     from_date: str = None,
@@ -357,7 +444,7 @@ async def list_messages(
     Retrieve messages with optional filters.
 
     Args:
-        chat_id: The ID of the chat to get messages from.
+        chat_id: The ID or username of the chat to get messages from.
         limit: Maximum number of messages to retrieve.
         search_query: Filter messages containing this text.
         from_date: Filter messages starting from this date (format: YYYY-MM-DD).
@@ -501,12 +588,13 @@ async def list_chats(chat_type: str = None, limit: int = 20) -> str:
 
 
 @mcp.tool()
-async def get_chat(chat_id: int) -> str:
+@validate_id('chat_id')
+async def get_chat(chat_id: Union[int, str]) -> str:
     """
     Get detailed information about a specific chat.
 
     Args:
-        chat_id: The ID of the chat.
+        chat_id: The ID or username of the chat.
     """
     try:
         entity = await client.get_entity(chat_id)
@@ -636,12 +724,13 @@ async def get_direct_chat_by_contact(contact_query: str) -> str:
 
 
 @mcp.tool()
-async def get_contact_chats(contact_id: int) -> str:
+@validate_id('contact_id')
+async def get_contact_chats(contact_id: Union[int, str]) -> str:
     """
     List all chats involving a specific contact.
 
     Args:
-        contact_id: The ID of the contact.
+        contact_id: The ID or username of the contact.
     """
     try:
         # Get contact info
@@ -688,12 +777,13 @@ async def get_contact_chats(contact_id: int) -> str:
 
 
 @mcp.tool()
-async def get_last_interaction(contact_id: int) -> str:
+@validate_id('contact_id')
+async def get_last_interaction(contact_id: Union[int, str]) -> str:
     """
     Get the most recent message with a contact.
 
     Args:
-        contact_id: The ID of the contact.
+        contact_id: The ID or username of the contact.
     """
     try:
         # Get contact info
@@ -724,12 +814,13 @@ async def get_last_interaction(contact_id: int) -> str:
 
 
 @mcp.tool()
-async def get_message_context(chat_id: int, message_id: int, context_size: int = 3) -> str:
+@validate_id('chat_id')
+async def get_message_context(chat_id: Union[int, str], message_id: int, context_size: int = 3) -> str:
     """
     Retrieve context around a specific message.
 
     Args:
-        chat_id: The ID of the chat.
+        chat_id: The ID or username of the chat.
         message_id: The ID of the central message.
         context_size: Number of messages before and after to include.
     """
@@ -841,11 +932,12 @@ async def add_contact(phone: str, first_name: str, last_name: str = "") -> str:
 
 
 @mcp.tool()
-async def delete_contact(user_id: int) -> str:
+@validate_id('user_id')
+async def delete_contact(user_id: Union[int, str]) -> str:
     """
     Delete a contact by user ID.
     Args:
-        user_id: The Telegram user ID of the contact to delete.
+        user_id: The Telegram user ID or username of the contact to delete.
     """
     try:
         user = await client.get_entity(user_id)
@@ -856,11 +948,12 @@ async def delete_contact(user_id: int) -> str:
 
 
 @mcp.tool()
-async def block_user(user_id: int) -> str:
+@validate_id('user_id')
+async def block_user(user_id: Union[int, str]) -> str:
     """
     Block a user by user ID.
     Args:
-        user_id: The Telegram user ID to block.
+        user_id: The Telegram user ID or username to block.
     """
     try:
         user = await client.get_entity(user_id)
@@ -871,11 +964,12 @@ async def block_user(user_id: int) -> str:
 
 
 @mcp.tool()
-async def unblock_user(user_id: int) -> str:
+@validate_id('user_id')
+async def unblock_user(user_id: Union[int, str]) -> str:
     """
     Unblock a user by user ID.
     Args:
-        user_id: The Telegram user ID to unblock.
+        user_id: The Telegram user ID or username to unblock.
     """
     try:
         user = await client.get_entity(user_id)
@@ -898,13 +992,14 @@ async def get_me() -> str:
 
 
 @mcp.tool()
-async def create_group(title: str, user_ids: list) -> str:
+@validate_id('user_ids')
+async def create_group(title: str, user_ids: List[Union[int, str]]) -> str:
     """
     Create a new group or supergroup and add users.
 
     Args:
         title: Title for the new group
-        user_ids: List of user IDs to add to the group
+        user_ids: List of user IDs or usernames to add to the group
     """
     try:
         # Convert user IDs to entities
@@ -956,13 +1051,14 @@ async def create_group(title: str, user_ids: list) -> str:
 
 
 @mcp.tool()
-async def invite_to_group(group_id: int, user_ids: list) -> str:
+@validate_id('group_id', 'user_ids')
+async def invite_to_group(group_id: Union[int, str], user_ids: List[Union[int, str]]) -> str:
     """
     Invite users to a group or channel.
 
     Args:
-        group_id: The ID of the group/channel.
-        user_ids: List of user IDs to invite.
+        group_id: The ID or username of the group/channel.
+        user_ids: List of user IDs or usernames to invite.
     """
     try:
         entity = await client.get_entity(group_id)
@@ -1005,12 +1101,13 @@ async def invite_to_group(group_id: int, user_ids: list) -> str:
 
 
 @mcp.tool()
-async def leave_chat(chat_id: int) -> str:
+@validate_id('chat_id')
+async def leave_chat(chat_id: Union[int, str]) -> str:
     """
     Leave a group or channel by chat ID.
 
     Args:
-        chat_id: The chat ID to leave.
+        chat_id: The chat ID or username to leave.
     """
     try:
         entity = await client.get_entity(chat_id)
@@ -1084,11 +1181,12 @@ async def leave_chat(chat_id: int) -> str:
 
 
 @mcp.tool()
-async def get_participants(chat_id: int) -> str:
+@validate_id('chat_id')
+async def get_participants(chat_id: Union[int, str]) -> str:
     """
     List all participants in a group or channel.
     Args:
-        chat_id: The group or channel ID.
+        chat_id: The group or channel ID or username.
     """
     try:
         participants = await client.get_participants(chat_id)
@@ -1102,11 +1200,12 @@ async def get_participants(chat_id: int) -> str:
 
 
 @mcp.tool()
-async def send_file(chat_id: int, file_path: str, caption: str = None) -> str:
+@validate_id('chat_id')
+async def send_file(chat_id: Union[int, str], file_path: str, caption: str = None) -> str:
     """
     Send a file to a chat.
     Args:
-        chat_id: The chat ID.
+        chat_id: The chat ID or username.
         file_path: Absolute path to the file to send (must exist and be readable).
         caption: Optional caption for the file.
     """
@@ -1125,11 +1224,12 @@ async def send_file(chat_id: int, file_path: str, caption: str = None) -> str:
 
 
 @mcp.tool()
-async def download_media(chat_id: int, message_id: int, file_path: str) -> str:
+@validate_id('chat_id')
+async def download_media(chat_id: Union[int, str], message_id: int, file_path: str) -> str:
     """
     Download media from a message in a chat.
     Args:
-        chat_id: The chat ID.
+        chat_id: The chat ID or username.
         message_id: The message ID containing the media.
         file_path: Absolute path to save the downloaded file (must be writable).
     """
@@ -1226,16 +1326,17 @@ async def get_privacy_settings() -> str:
 
 
 @mcp.tool()
+@validate_id('allow_users', 'disallow_users')
 async def set_privacy_settings(
-    key: str, allow_users: list = None, disallow_users: list = None
+    key: str, allow_users: Optional[List[Union[int, str]]] = None, disallow_users: Optional[List[Union[int, str]]] = None
 ) -> str:
     """
     Set privacy settings (e.g., last seen, phone, etc.).
 
     Args:
         key: The privacy setting to modify ('status' for last seen, 'phone', 'profile_photo', etc.)
-        allow_users: List of user IDs to allow
-        disallow_users: List of user IDs to disallow
+        allow_users: List of user IDs or usernames to allow
+        disallow_users: List of user IDs or usernames to disallow
     """
     try:
         # Import needed types
@@ -1382,7 +1483,8 @@ async def create_channel(title: str, about: str = "", megagroup: bool = False) -
 
 
 @mcp.tool()
-async def edit_chat_title(chat_id: int, title: str) -> str:
+@validate_id('chat_id')
+async def edit_chat_title(chat_id: Union[int, str], title: str) -> str:
     """
     Edit the title of a chat, group, or channel.
     """
@@ -1401,7 +1503,8 @@ async def edit_chat_title(chat_id: int, title: str) -> str:
 
 
 @mcp.tool()
-async def edit_chat_photo(chat_id: int, file_path: str) -> str:
+@validate_id('chat_id')
+async def edit_chat_photo(chat_id: Union[int, str], file_path: str) -> str:
     """
     Edit the photo of a chat, group, or channel. Requires a file path to an image.
     """
@@ -1434,7 +1537,8 @@ async def edit_chat_photo(chat_id: int, file_path: str) -> str:
 
 
 @mcp.tool()
-async def delete_chat_photo(chat_id: int) -> str:
+@validate_id('chat_id')
+async def delete_chat_photo(chat_id: Union[int, str]) -> str:
     """
     Delete the photo of a chat, group, or channel.
     """
@@ -1462,13 +1566,14 @@ async def delete_chat_photo(chat_id: int) -> str:
 
 
 @mcp.tool()
-async def promote_admin(group_id: int, user_id: int, rights: dict = None) -> str:
+@validate_id('group_id', 'user_id')
+async def promote_admin(group_id: Union[int, str], user_id: Union[int, str], rights: dict = None) -> str:
     """
     Promote a user to admin in a group/channel.
 
     Args:
-        group_id: ID of the group/channel
-        user_id: User ID to promote
+        group_id: ID or username of the group/channel
+        user_id: User ID or username to promote
         rights: Admin rights to give (optional)
     """
     try:
@@ -1526,13 +1631,14 @@ async def promote_admin(group_id: int, user_id: int, rights: dict = None) -> str
 
 
 @mcp.tool()
-async def demote_admin(group_id: int, user_id: int) -> str:
+@validate_id('group_id', 'user_id')
+async def demote_admin(group_id: Union[int, str], user_id: Union[int, str]) -> str:
     """
     Demote a user from admin in a group/channel.
 
     Args:
-        group_id: ID of the group/channel
-        user_id: User ID to demote
+        group_id: ID or username of the group/channel
+        user_id: User ID or username to demote
     """
     try:
         chat = await client.get_entity(group_id)
@@ -1574,13 +1680,14 @@ async def demote_admin(group_id: int, user_id: int) -> str:
 
 
 @mcp.tool()
-async def ban_user(chat_id: int, user_id: int) -> str:
+@validate_id('chat_id', 'user_id')
+async def ban_user(chat_id: Union[int, str], user_id: Union[int, str]) -> str:
     """
     Ban a user from a group or channel.
 
     Args:
-        chat_id: ID of the group/channel
-        user_id: User ID to ban
+        chat_id: ID or username of the group/channel
+        user_id: User ID or username to ban
     """
     try:
         chat = await client.get_entity(chat_id)
@@ -1620,13 +1727,14 @@ async def ban_user(chat_id: int, user_id: int) -> str:
 
 
 @mcp.tool()
-async def unban_user(chat_id: int, user_id: int) -> str:
+@validate_id('chat_id', 'user_id')
+async def unban_user(chat_id: Union[int, str], user_id: Union[int, str]) -> str:
     """
     Unban a user from a group or channel.
 
     Args:
-        chat_id: ID of the group/channel
-        user_id: User ID to unban
+        chat_id: ID or username of the group/channel
+        user_id: User ID or username to unban
     """
     try:
         chat = await client.get_entity(chat_id)
@@ -1666,7 +1774,8 @@ async def unban_user(chat_id: int, user_id: int) -> str:
 
 
 @mcp.tool()
-async def get_admins(chat_id: int) -> str:
+@validate_id('chat_id')
+async def get_admins(chat_id: Union[int, str]) -> str:
     """
     Get all admins in a group or channel.
     """
@@ -1684,7 +1793,8 @@ async def get_admins(chat_id: int) -> str:
 
 
 @mcp.tool()
-async def get_banned_users(chat_id: int) -> str:
+@validate_id('chat_id')
+async def get_banned_users(chat_id: Union[int, str]) -> str:
     """
     Get all banned users in a group or channel.
     """
@@ -1704,7 +1814,8 @@ async def get_banned_users(chat_id: int) -> str:
 
 
 @mcp.tool()
-async def get_invite_link(chat_id: int) -> str:
+@validate_id('chat_id')
+async def get_invite_link(chat_id: Union[int, str]) -> str:
     """
     Get the invite link for a group or channel.
     """
@@ -1807,7 +1918,8 @@ async def join_chat_by_link(link: str) -> str:
 
 
 @mcp.tool()
-async def export_chat_invite(chat_id: int) -> str:
+@validate_id('chat_id')
+async def export_chat_invite(chat_id: Union[int, str]) -> str:
     """
     Export a chat invite link.
     """
@@ -1896,11 +2008,12 @@ async def import_chat_invite(hash: str) -> str:
 
 
 @mcp.tool()
-async def send_voice(chat_id: int, file_path: str) -> str:
+@validate_id('chat_id')
+async def send_voice(chat_id: Union[int, str], file_path: str) -> str:
     """
     Send a voice message to a chat. File must be an OGG/OPUS voice note.
     Args:
-        chat_id: The chat ID.
+        chat_id: The chat ID or username.
         file_path: Absolute path to the OGG/OPUS file.
     """
     try:
@@ -1926,7 +2039,8 @@ async def send_voice(chat_id: int, file_path: str) -> str:
 
 
 @mcp.tool()
-async def forward_message(from_chat_id: int, message_id: int, to_chat_id: int) -> str:
+@validate_id('from_chat_id', 'to_chat_id')
+async def forward_message(from_chat_id: Union[int, str], message_id: int, to_chat_id: Union[int, str]) -> str:
     """
     Forward a message from one chat to another.
     """
@@ -1946,7 +2060,8 @@ async def forward_message(from_chat_id: int, message_id: int, to_chat_id: int) -
 
 
 @mcp.tool()
-async def edit_message(chat_id: int, message_id: int, new_text: str) -> str:
+@validate_id('chat_id')
+async def edit_message(chat_id: Union[int, str], message_id: int, new_text: str) -> str:
     """
     Edit a message you sent.
     """
@@ -1961,7 +2076,8 @@ async def edit_message(chat_id: int, message_id: int, new_text: str) -> str:
 
 
 @mcp.tool()
-async def delete_message(chat_id: int, message_id: int) -> str:
+@validate_id('chat_id')
+async def delete_message(chat_id: Union[int, str], message_id: int) -> str:
     """
     Delete a message by ID.
     """
@@ -1974,7 +2090,8 @@ async def delete_message(chat_id: int, message_id: int) -> str:
 
 
 @mcp.tool()
-async def pin_message(chat_id: int, message_id: int) -> str:
+@validate_id('chat_id')
+async def pin_message(chat_id: Union[int, str], message_id: int) -> str:
     """
     Pin a message in a chat.
     """
@@ -1987,7 +2104,8 @@ async def pin_message(chat_id: int, message_id: int) -> str:
 
 
 @mcp.tool()
-async def unpin_message(chat_id: int, message_id: int) -> str:
+@validate_id('chat_id')
+async def unpin_message(chat_id: Union[int, str], message_id: int) -> str:
     """
     Unpin a message in a chat.
     """
@@ -2000,7 +2118,8 @@ async def unpin_message(chat_id: int, message_id: int) -> str:
 
 
 @mcp.tool()
-async def mark_as_read(chat_id: int) -> str:
+@validate_id('chat_id')
+async def mark_as_read(chat_id: Union[int, str]) -> str:
     """
     Mark all messages as read in a chat.
     """
@@ -2013,7 +2132,8 @@ async def mark_as_read(chat_id: int) -> str:
 
 
 @mcp.tool()
-async def reply_to_message(chat_id: int, message_id: int, text: str) -> str:
+@validate_id('chat_id')
+async def reply_to_message(chat_id: Union[int, str], message_id: int, text: str) -> str:
     """
     Reply to a specific message in a chat.
     """
@@ -2028,11 +2148,12 @@ async def reply_to_message(chat_id: int, message_id: int, text: str) -> str:
 
 
 @mcp.tool()
-async def get_media_info(chat_id: int, message_id: int) -> str:
+@validate_id('chat_id')
+async def get_media_info(chat_id: Union[int, str], message_id: int) -> str:
     """
     Get info about media in a message.
     Args:
-        chat_id: The chat ID.
+        chat_id: The chat ID or username.
         message_id: The message ID.
     """
     try:
@@ -2058,7 +2179,8 @@ async def search_public_chats(query: str) -> str:
 
 
 @mcp.tool()
-async def search_messages(chat_id: int, query: str, limit: int = 20) -> str:
+@validate_id('chat_id')
+async def search_messages(chat_id: Union[int, str], query: str, limit: int = 20) -> str:
     """
     Search for messages in a chat by text.
     """
@@ -2094,7 +2216,8 @@ async def resolve_username(username: str) -> str:
 
 
 @mcp.tool()
-async def mute_chat(chat_id: int) -> str:
+@validate_id('chat_id')
+async def mute_chat(chat_id: Union[int, str]) -> str:
     """
     Mute notifications for a chat.
     """
@@ -2132,7 +2255,8 @@ async def mute_chat(chat_id: int) -> str:
 
 
 @mcp.tool()
-async def unmute_chat(chat_id: int) -> str:
+@validate_id('chat_id')
+async def unmute_chat(chat_id: Union[int, str]) -> str:
     """
     Unmute notifications for a chat.
     """
@@ -2170,7 +2294,8 @@ async def unmute_chat(chat_id: int) -> str:
 
 
 @mcp.tool()
-async def archive_chat(chat_id: int) -> str:
+@validate_id('chat_id')
+async def archive_chat(chat_id: Union[int, str]) -> str:
     """
     Archive a chat.
     """
@@ -2186,7 +2311,8 @@ async def archive_chat(chat_id: int) -> str:
 
 
 @mcp.tool()
-async def unarchive_chat(chat_id: int) -> str:
+@validate_id('chat_id')
+async def unarchive_chat(chat_id: Union[int, str]) -> str:
     """
     Unarchive a chat.
     """
@@ -2214,11 +2340,12 @@ async def get_sticker_sets() -> str:
 
 
 @mcp.tool()
-async def send_sticker(chat_id: int, file_path: str) -> str:
+@validate_id('chat_id')
+async def send_sticker(chat_id: Union[int, str], file_path: str) -> str:
     """
     Send a sticker to a chat. File must be a valid .webp sticker file.
     Args:
-        chat_id: The chat ID.
+        chat_id: The chat ID or username.
         file_path: Absolute path to the .webp sticker file.
     """
     try:
@@ -2291,11 +2418,12 @@ async def get_gif_search(query: str, limit: int = 10) -> str:
 
 
 @mcp.tool()
-async def send_gif(chat_id: int, gif_id: int) -> str:
+@validate_id('chat_id')
+async def send_gif(chat_id: Union[int, str], gif_id: int) -> str:
     """
     Send a GIF to a chat by Telegram GIF document ID (not a file path).
     Args:
-        chat_id: The chat ID.
+        chat_id: The chat ID or username.
         gif_id: Telegram document ID for the GIF (from get_gif_search).
     """
     try:
@@ -2393,7 +2521,8 @@ async def set_bot_commands(bot_username: str, commands: list) -> str:
 
 
 @mcp.tool()
-async def get_history(chat_id: int, limit: int = 100) -> str:
+@validate_id('chat_id')
+async def get_history(chat_id: Union[int, str], limit: int = 100) -> str:
     """
     Get full chat history (up to limit).
     """
@@ -2415,7 +2544,8 @@ async def get_history(chat_id: int, limit: int = 100) -> str:
 
 
 @mcp.tool()
-async def get_user_photos(user_id: int, limit: int = 10) -> str:
+@validate_id('user_id')
+async def get_user_photos(user_id: Union[int, str], limit: int = 10) -> str:
     """
     Get profile photos of a user.
     """
@@ -2430,7 +2560,8 @@ async def get_user_photos(user_id: int, limit: int = 10) -> str:
 
 
 @mcp.tool()
-async def get_user_status(user_id: int) -> str:
+@validate_id('user_id')
+async def get_user_status(user_id: Union[int, str]) -> str:
     """
     Get the online status of a user.
     """
@@ -2442,7 +2573,8 @@ async def get_user_status(user_id: int) -> str:
 
 
 @mcp.tool()
-async def get_recent_actions(chat_id: int) -> str:
+@validate_id('chat_id')
+async def get_recent_actions(chat_id: Union[int, str]) -> str:
     """
     Get recent admin actions (admin log) in a group or channel.
     """
@@ -2464,7 +2596,8 @@ async def get_recent_actions(chat_id: int) -> str:
 
 
 @mcp.tool()
-async def get_pinned_messages(chat_id: int) -> str:
+@validate_id('chat_id')
+async def get_pinned_messages(chat_id: Union[int, str]) -> str:
     """
     Get all pinned messages in a chat.
     """
diff --git a/session_string_generator.py b/session_string_generator.py
index 5647ab5..327e570 100755
--- a/session_string_generator.py
+++ b/session_string_generator.py
@@ -12,6 +12,11 @@ Usage:
 Requirements:
     - telethon
     - python-dotenv
+
+Note on ID Formats:
+When using the MCP server, please be aware that all `chat_id` and `user_id`
+parameters support integer IDs, string representations of IDs (e.g., "123456"),
+and usernames (e.g., "@mychannel").
 """
 
 import os
diff --git a/test_validation.py b/test_validation.py
new file mode 100644
index 0000000..6e7354b
--- /dev/null
+++ b/test_validation.py
@@ -0,0 +1,83 @@
+import pytest
+import os
+os.environ["TELEGRAM_API_ID"] = "12345"
+os.environ["TELEGRAM_API_HASH"] = "dummy_hash"
+from main import validate_id, ValidationError, log_and_format_error
+from functools import wraps
+import asyncio
+from typing import Union, List, Optional
+
+# A simple async function to be decorated for testing
+@validate_id('user_id', 'chat_id', 'user_ids')
+async def dummy_function(**kwargs):
+    return "success", kwargs
+
+@pytest.mark.asyncio
+async def test_valid_integer_id():
+    result, kwargs = await dummy_function(user_id=12345)
+    assert result == "success"
+    assert kwargs['user_id'] == 12345
+
+@pytest.mark.asyncio
+async def test_valid_negative_integer_id():
+    result, kwargs = await dummy_function(chat_id=-100123456)
+    assert result == "success"
+    assert kwargs['chat_id'] == -100123456
+
+@pytest.mark.asyncio
+async def test_valid_string_integer_id():
+    result, kwargs = await dummy_function(user_id="12345")
+    assert result == "success"
+    assert kwargs['user_id'] == 12345
+
+@pytest.mark.asyncio
+async def test_valid_username():
+    result, kwargs = await dummy_function(user_id="@test_user")
+    assert result == "success"
+    assert kwargs['user_id'] == "@test_user"
+
+@pytest.mark.asyncio
+async def test_valid_username_without_at():
+    result, kwargs = await dummy_function(user_id="test_user_long_enough")
+    assert result == "success"
+    assert kwargs['user_id'] == "test_user_long_enough"
+
+@pytest.mark.asyncio
+async def test_valid_list_of_ids():
+    result, kwargs = await dummy_function(user_ids=[123, "456", "@test_user"])
+    assert result == "success"
+    assert kwargs['user_ids'] == [123, 456, "@test_user"]
+
+@pytest.mark.asyncio
+async def test_invalid_float_id():
+    result = await dummy_function(user_id=123.45)
+    assert "Invalid user_id" in result
+    assert "Type must be an integer or a string" in result
+
+@pytest.mark.asyncio
+async def test_invalid_string_id():
+    result = await dummy_function(user_id="inv") # too short
+    assert "Invalid user_id" in result
+    assert "Must be a valid integer ID, or a username string" in result
+
+@pytest.mark.asyncio
+async def test_integer_out_of_range():
+    result = await dummy_function(user_id=2**64)
+    assert "Invalid user_id" in result
+    assert "out of the valid integer range" in result
+
+@pytest.mark.asyncio
+async def test_invalid_item_in_list():
+    result = await dummy_function(user_ids=[123, "456", 123.45])
+    assert "Invalid user_ids" in result
+    assert "Type must be an integer or a string" in result
+
+@pytest.mark.asyncio
+async def test_no_id_provided():
+    result, kwargs = await dummy_function()
+    assert result == "success"
+
+@pytest.mark.asyncio
+async def test_none_id_provided():
+    result, kwargs = await dummy_function(user_id=None)
+    assert result == "success"