Slack MCP Server

Instructions

Implementation Reference

• slack_mcp/server.py:849-890 (handler)

  The @mcp.tool()-decorated async function that defines and implements the 'send_list_message' MCP tool. It processes input parameters to build Slack Block Kit message blocks for a bulleted list and sends the message via SlackClient, returning the JSON result or error.

  @mcp.tool()
  async def send_list_message(
      channel: str,
      title: str,
      items: str,
      description: Optional[str] = None,
      thread_ts: Optional[str] = None
  ) -> str:
      """
      Send a formatted list message.
  
      Args:
          channel: Channel ID or name
          title: List title
          items: Newline or comma-separated list items
          description: Optional description text
          thread_ts: Thread timestamp for replies (optional)
      """
      try:
          blocks = [BlockKitBuilder.header(title)]
          
          if description:
              blocks.append(BlockKitBuilder.section(description))
              blocks.append(BlockKitBuilder.divider())
          
          # Process items
          if "\n" in items:
              item_list = [item.strip() for item in items.split("\n") if item.strip()]
          else:
              item_list = [item.strip() for item in items.split(",") if item.strip()]
          
          # Create formatted list
          formatted_items = "\n".join([f"• {item}" for item in item_list])
          blocks.append(BlockKitBuilder.section(formatted_items))
          
          fallback_text = f"{title}: {', '.join(item_list)}"
          
          client = SlackClient()
          result = await client.send_message(channel, fallback_text, thread_ts, blocks)
          return json.dumps(result, indent=2)
      except Exception as e:
          return json.dumps({"error": str(e)}, indent=2)

• slack_mcp/server.py:849-849 (registration)

  The @mcp.tool() decorator registers the send_list_message function as an MCP tool.

  @mcp.tool()

• slack_mcp/server.py:851-866 (schema)

  Input schema defined by type annotations and docstring Args description for the send_list_message tool.

      channel: str,
      title: str,
      items: str,
      description: Optional[str] = None,
      thread_ts: Optional[str] = None
  ) -> str:
      """
      Send a formatted list message.
  
      Args:
          channel: Channel ID or name
          title: List title
          items: Newline or comma-separated list items
          description: Optional description text
          thread_ts: Thread timestamp for replies (optional)
      """