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xlwings Excel MCP Server

merge_cells

Combine multiple cells into a single cell in Excel worksheets to create headers or organize data layouts.

Instructions

Merge a range of cells.

Args:
    sheet_name: Name of worksheet
    start_cell: Starting cell
    end_cell: Ending cell
    session_id: Session ID from open_workbook (preferred)
    filepath: Path to Excel file (legacy, deprecated)
    
Note: Use session_id for better performance. filepath parameter is deprecated.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
sheet_nameYes
start_cellYes
end_cellYes
session_idNo
filepathNo

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
resultYes

Implementation Reference

  • MCP tool registration and primary handler for 'merge_cells'. Handles session validation, dispatches to appropriate xlwings implementation based on session_id or filepath, and returns standardized response.
    def merge_cells(
        sheet_name: str,
        start_cell: str,
        end_cell: str,
        session_id: Optional[str] = None,
        filepath: Optional[str] = None
    ) -> str:
        """
        Merge a range of cells.
        
        Args:
            sheet_name: Name of worksheet
            start_cell: Starting cell
            end_cell: Ending cell
            session_id: Session ID from open_workbook (preferred)
            filepath: Path to Excel file (legacy, deprecated)
            
        Note: Use session_id for better performance. filepath parameter is deprecated.
        """
        try:
            # Support both new (session_id) and old (filepath) API
            if session_id:
                # New API: use session
                session = SESSION_MANAGER.get_session(session_id)
                if not session:
                    return ERROR_TEMPLATES['SESSION_NOT_FOUND'].format(
                        session_id=session_id, 
                        ttl=10  # Default TTL is 10 minutes (600 seconds)
                    )
                
                with session.lock:
                    from xlwings_mcp.xlwings_impl.range_xlw import merge_cells_xlw_with_wb
                    result = merge_cells_xlw_with_wb(session.workbook, sheet_name, start_cell, end_cell)
            elif filepath:
                # Legacy API: backwards compatibility
                logger.warning("Using deprecated filepath parameter. Please use session_id instead.")
                full_path = get_excel_path(filepath)
                from xlwings_mcp.xlwings_impl.range_xlw import merge_cells_xlw
                result = merge_cells_xlw(full_path, sheet_name, start_cell, end_cell)
            else:
                return ERROR_TEMPLATES['PARAMETER_MISSING'].format(
                    param1='session_id',
                    param2='filepath'
                )
            
            return result.get("message", "Cells merged successfully") if "error" not in result else f"Error: {result['error']}"
        except (ValidationError, SheetError) as e:
            return f"Error: {str(e)}"
        except Exception as e:
            logger.error(f"Error merging cells: {e}")
            raise
  • Core implementation for filepath-based merging using xlwings: opens workbook, validates sheet/range, performs merge_range.merge(), saves, and handles cleanup/errors.
    def merge_cells_xlw(filepath: str, sheet_name: str, start_cell: str, end_cell: str) -> Dict[str, Any]:
        """
        Merge cells in Excel using xlwings.
    
        Args:
            filepath: Path to Excel file
            sheet_name: Name of worksheet
            start_cell: Top-left cell of merge range
            end_cell: Bottom-right cell of merge range
    
        Returns:
            Dict with success message or error
        """
        app = None
        wb = None
    
        # Initialize COM for thread safety (Windows)
        _com_initialize()
    
        try:
            logger.info(f"Merging cells {start_cell}:{end_cell} in {sheet_name}")
    
            # Check if file exists
            if not os.path.exists(filepath):
                return {"error": f"File not found: {filepath}"}
    
            # Open Excel app and workbook
            app = xw.App(visible=False, add_book=False)
            wb = app.books.open(filepath)
            
            # Check if sheet exists
            sheet_names = [s.name for s in wb.sheets]
            if sheet_name not in sheet_names:
                return {"error": f"Sheet '{sheet_name}' not found"}
            
            sheet = wb.sheets[sheet_name]
            
            # Get the range to merge
            merge_range = sheet.range(f"{start_cell}:{end_cell}")
            
            # Check if range is already merged
            if merge_range.merge_cells:
                return {"error": f"Range {start_cell}:{end_cell} is already merged"}
            
            # Merge the cells
            merge_range.merge()
            
            # Save the workbook
            wb.save()
            
            logger.info(f"✅ Successfully merged cells {start_cell}:{end_cell}")
            return {
                "message": f"Successfully merged cells {start_cell}:{end_cell}",
                "range": f"{start_cell}:{end_cell}",
                "sheet": sheet_name
            }
            
        except Exception as e:
            logger.error(f"❌ Error merging cells: {str(e)}")
            return {"error": str(e)}
            
        finally:
            if wb:
                wb.close()
            if app:
                app.quit()
  • Session-based core implementation for merging using existing workbook: validates sheet/range, performs merge_range.merge(), saves workbook.
    def merge_cells_xlw_with_wb(wb, sheet_name: str, start_cell: str, end_cell: str) -> Dict[str, Any]:
        """
        Session-based cell merging using existing workbook object.
        
        Args:
            wb: Workbook object from session
            sheet_name: Name of worksheet
            start_cell: Top-left cell of merge range
            end_cell: Bottom-right cell of merge range
            
        Returns:
            Dict with success message or error
        """
        try:
            logger.info(f"🔗 Merging cells {start_cell}:{end_cell} in {sheet_name}")
            
            # Check if sheet exists
            sheet_names = [s.name for s in wb.sheets]
            if sheet_name not in sheet_names:
                return {"error": f"Sheet '{sheet_name}' not found"}
            
            sheet = wb.sheets[sheet_name]
            
            # Get the range to merge
            merge_range = sheet.range(f"{start_cell}:{end_cell}")
            
            # Check if range is already merged
            if merge_range.merge_cells:
                return {"error": f"Range {start_cell}:{end_cell} is already merged"}
            
            # Merge the cells
            merge_range.merge()
            
            # Save the workbook
            wb.save()
            
            logger.info(f"✅ Successfully merged cells {start_cell}:{end_cell}")
            return {
                "message": f"Successfully merged cells {start_cell}:{end_cell}",
                "range": f"{start_cell}:{end_cell}",
                "sheet": sheet_name
            }
            
        except Exception as e:
            logger.error(f"❌ Error merging cells: {str(e)}")
            return {"error": str(e)}
Behavior3/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations provided, the description carries the full burden. It clearly indicates this is a mutation operation ('Merge a range of cells'), but doesn't disclose important behavioral aspects like whether the merge is reversible, what happens to existing cell data, or if specific permissions are required. The performance note about session_id is helpful but insufficient for full transparency.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is perfectly structured with a clear purpose statement followed by parameter documentation and usage notes. Every sentence earns its place, with no wasted words. The information is front-loaded with the core functionality stated first.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given this is a mutation tool with no annotations but with an output schema (which handles return values), the description provides good coverage of the operation and parameters. However, for a destructive operation like cell merging, it should ideally mention data implications or refer to 'unmerge_cells' for reversal options.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

With 0% schema description coverage, the description compensates well by explaining all 5 parameters in the 'Args' section, including their purposes and usage guidance (session_id preferred, filepath deprecated). This adds significant value beyond the bare schema, though it doesn't provide format details like cell reference syntax.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the specific action ('Merge a range of cells') with the resource ('cells'), distinguishing it from sibling tools like 'unmerge_cells' which performs the opposite operation. The verb 'merge' is precise and unambiguous.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides clear context about parameter usage ('Use session_id for better performance. filepath parameter is deprecated'), which helps guide parameter selection. However, it doesn't explicitly state when to use this tool versus alternatives like 'format_range' or 'create_table' for similar spreadsheet operations.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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