Slack MCP Server

Instructions

Implementation Reference

• slack_mcp/server.py:387-407 (handler)

  MCP tool handler for upload_file: decorated with @mcp.tool(), parses input, calls SlackClient.upload_file, returns JSON result or error.

  @mcp.tool()
  async def upload_file(
      channels: str, content: str, filename: str, title: Optional[str] = None, initial_comment: Optional[str] = None
  ) -> str:
      """
      Upload a file to one or more Slack channels.
  
      Args:
          channels: Comma-separated list of channel IDs
          content: File content as text
          filename: Name for the file
          title: Title of the file
          initial_comment: Initial comment for the file
      """
      try:
          client = SlackClient()
          channels_list = channels.split(",")
          result = await client.upload_file(channels_list, content, filename, title, initial_comment)
          return json.dumps(result, indent=2)
      except Exception as e:
          return json.dumps({"error": str(e)}, indent=2)

• slack_mcp/server.py:158-175 (helper)

  SlackClient helper method that makes the actual Slack API call to files.upload with prepared parameters.

  async def upload_file(
      self,
      channels: List[str],
      content: str,
      filename: str,
      title: Optional[str] = None,
      initial_comment: Optional[str] = None,
  ) -> Dict[str, Any]:
      """Upload a file to one or more channels."""
      data = {"channels": ",".join(channels), "content": content, "filename": filename}
  
      if title:
          data["title"] = title
  
      if initial_comment:
          data["initial_comment"] = initial_comment
  
      return await self._make_request("POST", "files.upload", json_data=data)