list_columns

Instructions

Implementation Reference

• tools/sql_tools.py:96-118 (handler)

  The actual implementation of the list_columns method in the SQLTools class. It takes a table_name parameter, connects to MySQL, runs 'SHOW COLUMNS FROM `table_name`', and returns a formatted string listing each column's Field, Type, Null, Key, Default, and Extra attributes.

  def list_columns(self, table_name: str) -> str:
      """List columns for a given table.
      
      Args:
          table_name (str): Table name to inspect
      
      Returns:
          str: Column names and types for the table
      """
      with self.get_connection() as conn:
          cursor = conn.cursor(dictionary=True, buffered=True)
          cursor.execute(f"SHOW COLUMNS FROM `{table_name}`")
          columns = cursor.fetchall()
  
          if not columns:
              return f"No columns found for table '{table_name}'"
  
          output = [f"Columns for table '{table_name}':"]
          for column in columns:
              output.append(
                  f"{column['Field']} {column['Type']} NULL={column['Null']} KEY={column['Key']} DEFAULT={column['Default']} EXTRA={column['Extra']}"
              )
          return "\n".join(output)

• server.py:15-15 (registration)

  Registration of list_columns as an MCP tool via the FastMCP decorator pattern.

  mcp.tool()(sql_tools.list_columns)

• tools/sql_tools.py:96-104 (schema)

  The function signature serves as the schema: it accepts a single 'table_name: str' parameter and returns a 'str'.

  def list_columns(self, table_name: str) -> str:
      """List columns for a given table.
      
      Args:
          table_name (str): Table name to inspect
      
      Returns:
          str: Column names and types for the table
      """

• tools/sql_tools.py:19-43 (helper)

  The get_connection context manager is a helper used by list_columns to obtain a MySQL database connection.

  @contextmanager
  def get_connection(self):
      """Context manager for database connections.
      
      Yields:
          mysql.connector.connection: Database connection object
          
      Raises:
          Error: If connection to the database fails
      """
      connection = None
      try:
          connection = mysql.connector.connect(
              host=self.host,
              user=self.user,
              password=self.password,
              database=self.database
          )
          yield connection
      except Error as e:
          print(f"Error connecting to MySQL database: {e}")
          raise
      finally:
          if connection and connection.is_connected():
              connection.close()