Slack MCP Server

Instructions

Implementation Reference

• slack_mcp/server.py:980-1028 (handler)

  The send_form_message tool handler function. It is registered via the @mcp.tool() decorator and implements sending a Slack message with a Block Kit form containing a select menu.

  @mcp.tool()
  async def send_form_message(
      channel: str,
      title: str,
      description: str,
      select_options: str,
      select_placeholder: str = "Choose an option",
      select_action_id: str = "form_select",
      thread_ts: Optional[str] = None
  ) -> str:
      """
      Send a form-like message with a select menu.
  
      Args:
          channel: Channel ID or name
          title: Form title
          description: Form description
          select_options: JSON string of select options [{"text": "Option 1", "value": "opt1"}]
          select_placeholder: Placeholder text for select menu
          select_action_id: Action ID for the select menu
          thread_ts: Thread timestamp for replies (optional)
      """
      try:
          blocks = [
              BlockKitBuilder.header(title),
              BlockKitBuilder.section(description)
          ]
          
          # Parse select options
          options = json.loads(select_options)
          
          select_menu = BlockKitBuilder.select_menu(
              placeholder=select_placeholder,
              action_id=select_action_id,
              options=options
          )
          
          blocks.append(BlockKitBuilder.section_with_accessory(
              "Please make your selection:",
              select_menu
          ))
          
          fallback_text = f"{title}: {description}"
          
          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:659-681 (helper)

  BlockKitBuilder.select_menu method, a key helper used to create the interactive select menu element in the form message.

  def select_menu(placeholder: str, action_id: str, options: List[Dict[str, str]]) -> Dict[str, Any]:
      """Create a static select menu element."""
      return {
          "type": "static_select",
          "placeholder": {
              "type": "plain_text",
              "text": placeholder
          },
          "action_id": action_id,
          "options": [
              {
                  "text": {
                      "type": "plain_text",
                      "text": option["text"]
                  },
                  "value": option["value"]
              }
              for option in options
          ]
      }
  
  @staticmethod
  def section_with_accessory(text: str, accessory: Dict[str, Any], text_type: str = "mrkdwn") -> Dict[str, Any]:

• slack_mcp/server.py:681-691 (helper)

  BlockKitBuilder.section_with_accessory method, used to attach the select menu as an accessory to the section block.

  def section_with_accessory(text: str, accessory: Dict[str, Any], text_type: str = "mrkdwn") -> Dict[str, Any]:
      """Create a section block with an accessory element."""
      return {
          "type": "section",
          "text": {
              "type": text_type,
              "text": text
          },
          "accessory": accessory
      }