MCP Jupyter Server

Instructions

Implementation Reference

• src/jupyter-handler.js:600-618 (handler)

  The main handler function for the 'edit_cell' tool. Resolves cell by ID or index and delegates to editCellSource to update the notebook.

  async editCell(notebookPath, cellId, newSource) {
    const notebook = await this.readNotebook(notebookPath);
    
    // Find cell by ID or treat as index
    let cellIndex = -1;
    
    if (typeof cellId === 'string') {
      // Search by cell ID
      cellIndex = notebook.cells.findIndex(c => c.id === cellId);
      if (cellIndex === -1) {
        throw new Error(`Cell with ID '${cellId}' not found`);
      }
    } else {
      // Treat as index
      cellIndex = cellId;
    }
    
    return await this.editCellSource(notebookPath, cellIndex, newSource);
  }

• src/index.js:285-306 (schema)

  Input schema definition for the 'edit_cell' tool, used in the listTools response.

  {
    name: "edit_cell",
    description: "Edit the source code of a specific cell by ID or index",
    inputSchema: {
      type: "object",
      properties: {
        notebook_path: {
          type: "string",
          description: "Absolute path to the Jupyter notebook file"
        },
        cell_id: {
          type: ["string", "integer"],
          description: "Cell ID or zero-based index of the cell to edit"
        },
        new_source: {
          type: "string",
          description: "New source code for the cell"
        }
      },
      required: ["notebook_path", "cell_id", "new_source"]
    }
  },

• src/index.js:389-394 (registration)

  Dispatch registration in the CallToolRequestSchema handler that routes 'edit_cell' calls to JupyterHandler.editCell.

  case "edit_cell":
    return await this.jupyterHandler.editCell(
      args.notebook_path,
      args.cell_id,
      args.new_source
    );

• src/jupyter-handler.js:139-172 (helper)

  Core helper function that performs the actual editing of cell source by index, converting string to Jupyter source array format and writing the notebook.

  async editCellSource(notebookPath, cellIndex, newSource) {
    const notebook = await this.readNotebook(notebookPath);
    this.validateCellIndex(notebook.cells, cellIndex);
    
    // Convert string to array format - each line should end with \n except the last
    const lines = newSource.split('\n');
    const sourceArray = lines.map((line, index) => {
      // Add \n to all lines except the last one, unless the original ended with \n
      if (index === lines.length - 1) {
        // Last line: only add \n if original text ended with \n (detected by empty last element)
        return line === '' ? '' : line;
      } else {
        // All other lines get \n
        return line + '\n';
      }
    });
    
    // Remove empty last element if original ended with \n
    if (sourceArray.length > 1 && sourceArray[sourceArray.length - 1] === '') {
      sourceArray.pop();
    }
    
    notebook.cells[cellIndex].source = sourceArray;
    await this.writeNotebook(notebookPath, notebook);
    
    return {
      content: [
        {
          type: "text",
          text: `Successfully updated cell ${cellIndex}`
        }
      ]
    };
  }