diff --git a/index.d.ts b/index.d.ts
index 4e4eb06..6af7911 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -3,9 +3,15 @@
 // Definitions by: themauveavenger <https://github.com/themauveavenger/>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
 
+/** Attempts to read filename and parse */
 export declare function readFile(filename: string, opts?: IParsingOptions): IWorkBook;
+/** Attempts to parse data */
 export declare function read(data: any, opts?: IParsingOptions): IWorkBook;
-export declare function write(data: any, opts?: IParsingOptions): any;
+/** Attempts to write workbook data to filename */
+export declare function writeFile(data: IWorkBook, filename: string, opts?: IWritingOptions): any;
+/** Attempts to write the workbook data */
+export declare function write(data: IWorkBook, opts?: IWritingOptions): any;
+
 export declare var utils: IUtils;
 
 export interface IProperties {
@@ -27,25 +33,125 @@ export interface IProperties {
 }
 
 export interface IParsingOptions {
-    cellFormula?: boolean;
-    cellHTML?: boolean;
-    cellNF?: boolean;
-    cellStyles?: boolean;
-    cellDates?: boolean;
-    sheetStubs?: boolean;
-    sheetRows?: number;
-    bookDeps?: boolean;
-    bookFiles?: boolean;
-    bookProps?: boolean;
-    bookSheets?: boolean;
-    bookVBA?: boolean;
-    password?: string;
-    bookType?: string;
+    /**
+     * Input data encoding
+     */
+    type?: 'base64' | 'binary' | 'buffer' | 'array' | 'file';
 
     /**
-     * Possible options: 'binary', 'base64', 'buffer', 'file'
+     * Save formulae to the .f field
+     * @default true
      */
-    type?: string;
+    cellFormula?: boolean;
+
+    /**
+     * Parse rich text and save HTML to the .h field
+     * @default true
+     */
+    cellHTML?: boolean;
+
+    /**
+     * Save number format string to the .z field
+     * @default false
+     */
+    cellNF?: boolean;
+
+    /**
+     * Save style/theme info to the .s field
+     * @default false
+     */
+    cellStyles?: boolean;
+
+    /**
+     * Store dates as type d (default is n)
+     * @default false
+     */
+    cellDates?: boolean;
+
+    /**
+     * Create cell objects for stub cells
+     * @default false
+     */
+    sheetStubs?: boolean;
+
+    /**
+     * If >0, read the first sheetRows rows
+     * @default 0
+     */
+    sheetRows?: number;
+
+    /**
+     * If true, parse calculation chains
+     * @default false
+     */
+    bookDeps?: boolean;
+
+    /**
+     * If true, add raw files to book object
+     * @default false
+     */
+    bookFiles?: boolean;
+
+    /**
+     * If true, only parse enough to get book metadata
+     * @default false
+     */
+    bookProps?: boolean;
+
+    /**
+     * If true, only parse enough to get the sheet names
+     * @default false
+     */
+    bookSheets?: boolean;
+
+    /**
+     * If true, expose vbaProject.bin to vbaraw field
+     * @default false
+     */
+    bookVBA?: boolean;
+
+    /**
+     * If defined and file is encrypted, use password
+     * @default ''
+     */
+    password?: string;
+}
+
+export interface IWritingOptions {
+    /**
+     * Output data encoding
+     */
+    type?: 'base64' | 'binary' | 'buffer' | 'file';
+
+    /**
+     * Store dates as type d (default is n)
+     * @default false
+     */
+    cellDates?: boolean;
+
+    /**
+     * Generate Shared String Table
+     * @default false
+     */
+    bookSST?: boolean;
+
+    /**
+     * Type of Workbook
+     * @default 'xlsx'
+     */
+    bookType?: 'xlsx' | 'xlsm' | 'xlsb' | 'ods' | 'biff2' | 'fods' | 'csv';
+
+    /**
+     * Name of Worksheet for single-sheet formats
+     * @default ''
+     */
+    sheet?: string;
+
+    /**
+     * Use ZIP compression for ZIP-based formats
+     * @default false
+     */
+    compression?: boolean;
 }
 
 export interface IWorkBook {
@@ -75,19 +181,34 @@ export interface IWorkSheet {
 }
 
 export interface IWorkSheetCell {
-    /**
-     * The Excel Data Type of the cell.
-     * b Boolean, n Number, e error, s String, d Date
-     */
-    t: string;
-
     /**
      * The raw value of the cell.
      */
-    v: string;
+    v: string | number | boolean | Date;
 
     /**
-     * rich text encoding (if applicable)
+     * Formatted text (if applicable)
+     */
+    w?: string;
+
+    /**
+    * The Excel Data Type of the cell.
+    * b Boolean, n Number, e error, s String, d Date
+    */
+    t: 'b' | 'n' | 'e' | 's' | 'd';
+
+    /**
+     * Cell formula (if applicable)
+     */
+    f?: string;
+
+    /**
+     * Range of enclosing array if formula is array formula (if applicable)
+     */
+    F?: string;
+
+    /**
+     * Rich text encoding (if applicable)
      */
     r?: string;
 
@@ -97,56 +218,67 @@ export interface IWorkSheetCell {
     h?: string;
 
     /**
-     * formatted text (if applicable)
-     */
-    w?: string;
-
-    /**
-     * cell formula (if applicable)
-     */
-    f?: string;
-
-    /**
-     * comments associated with the cell **
+     * Comments associated with the cell **
      */
     c?: string;
 
     /**
-     * number format string associated with the cell (if requested)
+     * Number format string associated with the cell (if requested)
      */
     z?: string;
 
     /**
-     * cell hyperlink object (.Target holds link, .tooltip is tooltip)
+     * Cell hyperlink object (.Target holds link, .tooltip is tooltip)
      */
-    l?: string;
+    l?: string | Object;
 
     /**
-     * the style/theme of the cell (if applicable)
+     * The style/theme of the cell (if applicable)
      */
     s?: string;
 }
 
 export interface ICell {
+    /** Column number */
     c: number;
+    /** Row number */
     r: number;
 }
 
 export interface IRange {
+    /** Starting cell */
     s: ICell;
+    /** Ending cell */
     e: ICell;
 }
 
 export interface IUtils {
+    /** Converts a worksheet object to an array of JSON objects */
     sheet_to_json<T>(worksheet:IWorkSheet, opts?: {
         raw?: boolean;
         range?: any;
         header?: "A"|number|string[];
     }):T[];
+    /** Generates delimiter-separated-values output */
     sheet_to_csv(worksheet: IWorkSheet, options?: { FS: string, RS: string }): string;
+    /** Generates a list of the formulae (with value fallbacks) */
     sheet_to_formulae(worksheet: IWorkSheet):any;
-    encode_cell(cell: ICell): any;
-    encode_range(s: ICell, e: ICell): any;
+
+    /** Converts 0-indexed cell address to A1 form */
+    encode_cell(cell: ICell): string;
+    /** Converts 0-indexed row to A1 form */
+    encode_row(row: number): string;
+    /** Converts 0-indexed column to A1 form */
+    encode_col(col: number): string;
+    /** Converts 0-indexed range to A1 form */
+    encode_range(s: ICell, e: ICell): string;
+
+    /** Converts A1 cell address to 0-indexed form */
     decode_cell(address: string): ICell;
+    /** Converts A1 row to 0-indexed form */
+    decode_row(row: string): number;
+    /** Converts A1 column to 0-indexed form */
+    decode_col(col: string): number;
+    /** Converts A1 range to 0-indexed form */
     decode_range(range: string): IRange;
 }