diff --git a/package-lock.json b/package-lock.json
index 8647a1367c2e..bf463116201b 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -17,6 +17,7 @@
         "@types/ws": "^8.2.0",
         "discord-api-types": "^0.24.0",
         "node-fetch": "^2.6.1",
+        "type-fest": "^2.5.3",
         "ws": "^8.2.3"
       },
       "devDependencies": {
@@ -5861,20 +5862,6 @@
       "integrity": "sha1-FQStJSMVjKpA20onh8sBQRmU6k8=",
       "dev": true
     },
-    "node_modules/fsevents": {
-      "version": "2.3.2",
-      "resolved": "https://registry.npmjs.org/fsevents/-/fsevents-2.3.2.tgz",
-      "integrity": "sha512-xiqMQR4xAeHTuB9uWm+fFRcIOgKBMiOBP+eXiyT7jsgVCq1bkVygt00oASowB7EdtpOHaaPgKt812P9ab+DDKA==",
-      "dev": true,
-      "hasInstallScript": true,
-      "optional": true,
-      "os": [
-        "darwin"
-      ],
-      "engines": {
-        "node": "^8.16.0 || ^10.6.0 || >=11.0.0"
-      }
-    },
     "node_modules/fstream": {
       "version": "1.0.12",
       "resolved": "https://registry.npmjs.org/fstream/-/fstream-1.0.12.tgz",
@@ -6454,6 +6441,18 @@
         "url": "https://github.com/sponsors/sindresorhus"
       }
     },
+    "node_modules/globals/node_modules/type-fest": {
+      "version": "0.20.2",
+      "resolved": "https://registry.npmjs.org/type-fest/-/type-fest-0.20.2.tgz",
+      "integrity": "sha512-Ne+eE4r0/iWnpAxD852z3A+N0Bt5RN//NjJwRd2VFHEmrywxf5vsZlh4R6lixl6B+wz/8d+maTSAkN1FIkI3LQ==",
+      "dev": true,
+      "engines": {
+        "node": ">=10"
+      },
+      "funding": {
+        "url": "https://github.com/sponsors/sindresorhus"
+      }
+    },
     "node_modules/globby": {
       "version": "11.0.4",
       "resolved": "https://registry.npmjs.org/globby/-/globby-11.0.4.tgz",
@@ -9727,17 +9726,6 @@
         "url": "https://github.com/sponsors/sindresorhus"
       }
     },
-    "node_modules/ow/node_modules/type-fest": {
-      "version": "2.5.2",
-      "resolved": "https://registry.npmjs.org/type-fest/-/type-fest-2.5.2.tgz",
-      "integrity": "sha512-WMbytmAs5PUTqwGJRE+WoRrD2S0bYFtHX8k4Y/1l18CG5kqA3keJud9pPQ/r30FE9n8XRFCXF9BbccHIZzRYJw==",
-      "engines": {
-        "node": ">=12.20"
-      },
-      "funding": {
-        "url": "https://github.com/sponsors/sindresorhus"
-      }
-    },
     "node_modules/p-limit": {
       "version": "3.1.0",
       "resolved": "https://registry.npmjs.org/p-limit/-/p-limit-3.1.0.tgz",
@@ -11368,6 +11356,7 @@
       "version": "2.2.2",
       "resolved": "https://registry.npmjs.org/tar/-/tar-2.2.2.tgz",
       "integrity": "sha512-FCEhQ/4rE1zYv9rYXJw/msRqsnmlje5jHP6huWeBZ704jUTy02c5AZyWujpMR1ax6mVw9NyJMfuK2CMDWVIfgA==",
+      "deprecated": "This version of tar is no longer supported, and will not receive security updates. Please upgrade asap.",
       "dev": true,
       "dependencies": {
         "block-stream": "*",
@@ -12044,12 +12033,11 @@
       }
     },
     "node_modules/type-fest": {
-      "version": "0.20.2",
-      "resolved": "https://registry.npmjs.org/type-fest/-/type-fest-0.20.2.tgz",
-      "integrity": "sha512-Ne+eE4r0/iWnpAxD852z3A+N0Bt5RN//NjJwRd2VFHEmrywxf5vsZlh4R6lixl6B+wz/8d+maTSAkN1FIkI3LQ==",
-      "dev": true,
+      "version": "2.6.0",
+      "resolved": "https://registry.npmjs.org/type-fest/-/type-fest-2.6.0.tgz",
+      "integrity": "sha512-XN1FDGGtaSDA6CFsCW5iolTQqFsnJ+ZF6JqSz0SqXoh4F8GY0xqUv5RYnTilpmL+sOH8OH4FX8tf9YyAPM2LDA==",
       "engines": {
-        "node": ">=10"
+        "node": ">=12.20"
       },
       "funding": {
         "url": "https://github.com/sponsors/sindresorhus"
@@ -17193,13 +17181,6 @@
       "integrity": "sha1-FQStJSMVjKpA20onh8sBQRmU6k8=",
       "dev": true
     },
-    "fsevents": {
-      "version": "2.3.2",
-      "resolved": "https://registry.npmjs.org/fsevents/-/fsevents-2.3.2.tgz",
-      "integrity": "sha512-xiqMQR4xAeHTuB9uWm+fFRcIOgKBMiOBP+eXiyT7jsgVCq1bkVygt00oASowB7EdtpOHaaPgKt812P9ab+DDKA==",
-      "dev": true,
-      "optional": true
-    },
     "fstream": {
       "version": "1.0.12",
       "resolved": "https://registry.npmjs.org/fstream/-/fstream-1.0.12.tgz",
@@ -17647,6 +17628,14 @@
       "dev": true,
       "requires": {
         "type-fest": "^0.20.2"
+      },
+      "dependencies": {
+        "type-fest": {
+          "version": "0.20.2",
+          "resolved": "https://registry.npmjs.org/type-fest/-/type-fest-0.20.2.tgz",
+          "integrity": "sha512-Ne+eE4r0/iWnpAxD852z3A+N0Bt5RN//NjJwRd2VFHEmrywxf5vsZlh4R6lixl6B+wz/8d+maTSAkN1FIkI3LQ==",
+          "dev": true
+        }
       }
     },
     "globby": {
@@ -20147,11 +20136,6 @@
           "requires": {
             "is-obj": "^2.0.0"
           }
-        },
-        "type-fest": {
-          "version": "2.5.2",
-          "resolved": "https://registry.npmjs.org/type-fest/-/type-fest-2.5.2.tgz",
-          "integrity": "sha512-WMbytmAs5PUTqwGJRE+WoRrD2S0bYFtHX8k4Y/1l18CG5kqA3keJud9pPQ/r30FE9n8XRFCXF9BbccHIZzRYJw=="
         }
       }
     },
@@ -21930,10 +21914,9 @@
       "dev": true
     },
     "type-fest": {
-      "version": "0.20.2",
-      "resolved": "https://registry.npmjs.org/type-fest/-/type-fest-0.20.2.tgz",
-      "integrity": "sha512-Ne+eE4r0/iWnpAxD852z3A+N0Bt5RN//NjJwRd2VFHEmrywxf5vsZlh4R6lixl6B+wz/8d+maTSAkN1FIkI3LQ==",
-      "dev": true
+      "version": "2.6.0",
+      "resolved": "https://registry.npmjs.org/type-fest/-/type-fest-2.6.0.tgz",
+      "integrity": "sha512-XN1FDGGtaSDA6CFsCW5iolTQqFsnJ+ZF6JqSz0SqXoh4F8GY0xqUv5RYnTilpmL+sOH8OH4FX8tf9YyAPM2LDA=="
     },
     "typedarray": {
       "version": "0.0.6",
diff --git a/package.json b/package.json
index 1a73c0053135..6ba8da221f33 100644
--- a/package.json
+++ b/package.json
@@ -57,6 +57,7 @@
     "@types/ws": "^8.2.0",
     "discord-api-types": "^0.24.0",
     "node-fetch": "^2.6.1",
+    "type-fest": "^2.5.3",
     "ws": "^8.2.3"
   },
   "devDependencies": {
diff --git a/tslint.json b/tslint.json
index d66f7bdf3b60..151105a8b488 100644
--- a/tslint.json
+++ b/tslint.json
@@ -24,6 +24,7 @@
     "array-type": [true, "array"],
     "one-line": false,
     "no-any-union": false,
-    "void-return": false
+    "void-return": false,
+    "unified-signatures": false
   }
 }
diff --git a/typings/index.d.ts b/typings/index.d.ts
index 66128dba8ec1..caf703c903c3 100644
--- a/typings/index.d.ts
+++ b/typings/index.d.ts
@@ -45,6 +45,7 @@ import {
   APIUser,
   GatewayVoiceServerUpdateDispatchData,
   GatewayVoiceStateUpdateDispatchData,
+  RESTPatchAPIApplicationCommandJSONBody,
   RESTPostAPIApplicationCommandsJSONBody,
   Snowflake,
 } from 'discord-api-types/v9';
@@ -137,6 +138,7 @@ import {
   RawWidgetData,
   RawWidgetMemberData,
 } from './rawDataTypes';
+import type { CamelCasedPropertiesDeep } from 'type-fest';
 
 //#region Classes
 
@@ -213,7 +215,7 @@ export class ApplicationCommand<PermissionsFetchType = {}> extends Base {
   public readonly manager: ApplicationCommandManager;
   public id: Snowflake;
   public name: string;
-  public options: ApplicationCommandOption[];
+  public options: Camelize<APIApplicationCommandOption>[];
   public permissions: ApplicationCommandPermissionsManager<
     PermissionsFetchType,
     PermissionsFetchType,
@@ -224,23 +226,29 @@ export class ApplicationCommand<PermissionsFetchType = {}> extends Base {
   public type: ApplicationCommandType;
   public version: Snowflake;
   public delete(): Promise<ApplicationCommand<PermissionsFetchType>>;
+  /** @deprecated use `edit(Camelize<RESTPatchAPIApplicationCommandJSONBody>)` instead */
   public edit(data: ApplicationCommandData): Promise<ApplicationCommand<PermissionsFetchType>>;
+  public edit(
+    data: Camelize<RESTPatchAPIApplicationCommandJSONBody>,
+  ): Promise<ApplicationCommand<PermissionsFetchType>>;
   public equals(
-    command: ApplicationCommand | ApplicationCommandData | RawApplicationCommandData,
+    command: ApplicationCommand | Camelize<RESTPatchAPIApplicationCommandJSONBody> | RawApplicationCommandData,
     enforceOptionorder?: boolean,
   ): boolean;
   public static optionsEqual(
-    existing: ApplicationCommandOption[],
-    options: ApplicationCommandOption[] | ApplicationCommandOptionData[] | APIApplicationCommandOption[],
+    existing: Camelize<APIApplicationCommandOption>[],
+    options: Camelize<APIApplicationCommandOption>[] | APIApplicationCommandOption[],
     enforceOptionorder?: boolean,
   ): boolean;
   private static _optionEquals(
-    existing: ApplicationCommandOption,
-    options: ApplicationCommandOption | ApplicationCommandOptionData | APIApplicationCommandOption,
+    existing: Camelize<APIApplicationCommandOption>[],
+    options: Camelize<APIApplicationCommandOption>[] | APIApplicationCommandOption,
     enforceOptionorder?: boolean,
   ): boolean;
-  private static transformOption(option: ApplicationCommandOptionData, received?: boolean): unknown;
-  private static transformCommand(command: ApplicationCommandData): RESTPostAPIApplicationCommandsJSONBody;
+  private static transformOption(option: Camelize<APIApplicationCommandOption>, received?: boolean): unknown;
+  private static transformCommand(
+    command: Camelize<RESTPostAPIApplicationCommandsJSONBody>,
+  ): RESTPostAPIApplicationCommandsJSONBody;
   private static isAPICommandData(command: object): command is RESTPostAPIApplicationCommandsJSONBody;
 }
 
@@ -2336,10 +2344,8 @@ export class WebhookClient extends WebhookMixin(BaseClient) {
     options: string | MessagePayload | WebhookEditMessageOptions,
   ): Promise<APIMessage>;
   public fetchMessage(message: Snowflake, options?: WebhookFetchMessageOptions): Promise<APIMessage>;
-  /* tslint:disable:unified-signatures */
   /** @deprecated */
   public fetchMessage(message: Snowflake, cache?: boolean): Promise<APIMessage>;
-  /* tslint:enable:unified-signatures */
   public send(options: string | MessagePayload | WebhookMessageOptions): Promise<APIMessage>;
 }
 
@@ -2640,7 +2646,9 @@ export abstract class CachedManager<K, Holds, R> extends DataManager<K, Holds, R
   private _add(data: unknown, cache?: boolean, { id, extras }?: { id: K; extras: unknown[] }): Holds;
 }
 
-export type ApplicationCommandDataResolvable = ApplicationCommandData | RESTPostAPIApplicationCommandsJSONBody;
+export type ApplicationCommandDataResolvable =
+  | Camelize<RESTPostAPIApplicationCommandsJSONBody>
+  | RESTPostAPIApplicationCommandsJSONBody;
 
 export class ApplicationCommandManager<
   ApplicationCommandScope = ApplicationCommand<{ guild: GuildResolvable }>,
@@ -2656,7 +2664,18 @@ export class ApplicationCommandManager<
     null
   >;
   private commandPath({ id, guildId }: { id?: Snowflake; guildId?: Snowflake }): unknown;
+  /** @deprecated use `create(ApplicationCommandDataResolvable)` instead */
+  public create(
+    command: ApplicationCommandData | RESTPostAPIApplicationCommandsJSONBody,
+  ): Promise<ApplicationCommandScope>;
+  /** @deprecated use `create(ApplicationCommandDataResolvable, Snowflake)` instead */
+  public create(
+    command: ApplicationCommandData | RESTPostAPIApplicationCommandsJSONBody,
+    guildId: Snowflake,
+  ): Promise<ApplicationCommand>;
   public create(command: ApplicationCommandDataResolvable, guildId?: Snowflake): Promise<ApplicationCommandScope>;
+  /** @deprecated use `delete(ApplicationCommandDataResolvable, Snowflake?)` instead */
+  public delete(command: ApplicationCommandData, guildId?: Snowflake): Promise<ApplicationCommandScope | null>;
   public delete(command: ApplicationCommandResolvable, guildId?: Snowflake): Promise<ApplicationCommandScope | null>;
   public edit(
     command: ApplicationCommandResolvable,
@@ -2677,13 +2696,20 @@ export class ApplicationCommandManager<
     id?: Snowflake,
     options?: FetchApplicationCommandOptions,
   ): Promise<Collection<Snowflake, ApplicationCommandScope>>;
+  /** @deprecated Use `set(ApplicationCommandResolvable)` instead */
+  public set(commands: ApplicationCommandData[]): Promise<Collection<Snowflake, ApplicationCommandScope>>;
+  /** @deprecated Use `set(ApplicationCommandResolvable, Snowflake)` instead */
+  public set(
+    commands: ApplicationCommandData[],
+    guildId: Snowflake,
+  ): Promise<Collection<Snowflake, ApplicationCommand>>;
   public set(commands: ApplicationCommandDataResolvable[]): Promise<Collection<Snowflake, ApplicationCommandScope>>;
   public set(
     commands: ApplicationCommandDataResolvable[],
     guildId: Snowflake,
   ): Promise<Collection<Snowflake, ApplicationCommand>>;
   private static transformCommand(
-    command: ApplicationCommandData,
+    command: Camelize<RESTPostAPIApplicationCommandsJSONBody>,
   ): Omit<APIApplicationCommand, 'id' | 'application_id' | 'guild_id'>;
 }
 
@@ -2748,7 +2774,9 @@ export class GuildApplicationCommandManager extends ApplicationCommandManager<Ap
   private constructor(guild: Guild, iterable?: Iterable<RawApplicationCommandData>);
   public guild: Guild;
   public create(command: ApplicationCommandDataResolvable): Promise<ApplicationCommand>;
-  public delete(command: ApplicationCommandResolvable): Promise<ApplicationCommand | null>;
+  /** @deprecated use `delete(ApplicationCommandDataResolvable, Snowflake?)` instead */
+  public delete(command: ApplicationCommandData, guildId?: Snowflake): Promise<ApplicationCommand | null>;
+  public delete(command: ApplicationCommandResolvable, guildId?: Snowflake): Promise<ApplicationCommand | null>;
   public edit(
     command: ApplicationCommandResolvable,
     data: ApplicationCommandDataResolvable,
@@ -2756,6 +2784,8 @@ export class GuildApplicationCommandManager extends ApplicationCommandManager<Ap
   public fetch(id: Snowflake, options?: BaseFetchOptions): Promise<ApplicationCommand>;
   public fetch(options: BaseFetchOptions): Promise<Collection<Snowflake, ApplicationCommand>>;
   public fetch(id?: undefined, options?: BaseFetchOptions): Promise<Collection<Snowflake, ApplicationCommand>>;
+  /** @deprecated Use `set(ApplicationCommandResolvable)` instead */
+  public set(commands: ApplicationCommandData[]): Promise<Collection<Snowflake, ApplicationCommand>>;
   public set(commands: ApplicationCommandDataResolvable[]): Promise<Collection<Snowflake, ApplicationCommand>>;
 }
 
@@ -3074,10 +3104,8 @@ export interface PartialWebhookFields {
     options: string | MessagePayload | WebhookEditMessageOptions,
   ): Promise<Message | APIMessage>;
   fetchMessage(message: Snowflake | '@original', options?: WebhookFetchMessageOptions): Promise<Message | APIMessage>;
-  /* tslint:disable:unified-signatures */
   /** @deprecated */
   fetchMessage(message: Snowflake | '@original', cache?: boolean): Promise<Message | APIMessage>;
-  /* tslint:enable:unified-signatures */
   send(options: string | MessagePayload | WebhookMessageOptions): Promise<Message | APIMessage>;
 }
 
@@ -3343,6 +3371,7 @@ export interface ChatInputApplicationCommandData extends BaseApplicationCommandD
   options?: ApplicationCommandOptionData[];
 }
 
+/** @deprecated use `Camelize<RESTPostApplicationCommandBody>` instead */
 export type ApplicationCommandData =
   | UserApplicationCommandData
   | MessageApplicationCommandData
@@ -3430,6 +3459,10 @@ export interface ApplicationCommandNonOptions extends BaseApplicationCommandOpti
   type: Exclude<CommandOptionNonChoiceResolvableType, ApplicationCommandOptionTypes>;
 }
 
+// Type alias since the lib name is very long.
+export type Camelize<T> = CamelCasedPropertiesDeep<T>;
+
+/** @deprecated Use `Camelize<APIApplicationCommandsOption>` instead. */
 export type ApplicationCommandOptionData =
   | ApplicationCommandSubGroupData
   | ApplicationCommandNonOptionsData
@@ -3439,6 +3472,7 @@ export type ApplicationCommandOptionData =
   | ApplicationCommandNumericOptionData
   | ApplicationCommandSubCommandData;
 
+/** @deprecated use `Camelize<APIApplicationCommandOption>` instead */
 export type ApplicationCommandOption =
   | ApplicationCommandSubGroup
   | ApplicationCommandNonOptions
diff --git a/typings/index.test-d.ts b/typings/index.test-d.ts
index 9eb72d8e9bfd..cbaf73061d12 100644
--- a/typings/index.test-d.ts
+++ b/typings/index.test-d.ts
@@ -1,5 +1,4 @@
-import type { ChildProcess } from 'child_process';
-import type {
+import {
   APIInteractionGuildMember,
   APIMessage,
   APIPartialChannel,
@@ -7,15 +6,21 @@ import type {
   APIInteractionDataResolvedGuildMember,
   APIInteractionDataResolvedChannel,
   APIRole,
+  ChannelType,
+  ApplicationCommandOptionType,
+  APIApplicationCommand,
+  APIApplicationCommandOption,
+  APIApplicationCommandSubCommandOptions,
 } from 'discord-api-types/v9';
+import type { ChildProcess } from 'node:child_process';
 import {
   ApplicationCommand,
-  ApplicationCommandData,
+  ApplicationCommandChannelOptionData,
+  ApplicationCommandChoicesData,
   ApplicationCommandManager,
-  ApplicationCommandOptionData,
+  ApplicationCommandNonOptionsData,
   ApplicationCommandResolvable,
   ApplicationCommandSubCommandData,
-  ApplicationCommandSubGroupData,
   BaseCommandInteraction,
   ButtonInteraction,
   CacheType,
@@ -28,7 +33,6 @@ import {
   CommandInteraction,
   CommandInteractionOption,
   CommandInteractionOptionResolver,
-  CommandOptionNonChoiceResolvableType,
   Constants,
   ContextMenuInteraction,
   DMChannel,
@@ -77,6 +81,9 @@ import {
   User,
   VoiceChannel,
   Shard,
+  Camelize,
+  ApplicationCommandAutocompleteOption,
+  ApplicationCommandNumericOptionData,
   WebSocketShard,
   Collector,
 } from '.';
@@ -686,6 +693,20 @@ client.login('absolutely-valid-token');
 // Test client conditional types
 client.on('ready', client => {
   expectType<Client<true>>(client);
+
+  // Test camelized post command data.
+  client.application.commands.create({
+    name: 'Foo',
+    description: 'Bar',
+    options: [
+      {
+        name: 'test',
+        description: 'test',
+        type: ApplicationCommandOptionType.Channel,
+        channelTypes: [ChannelType.GuildCategory],
+      },
+    ],
+  });
 });
 
 declare const loggedInClient: Client<true>;
@@ -783,7 +804,7 @@ expectType<1>(Constants.Status.CONNECTING);
 expectType<0>(Constants.Opcodes.DISPATCH);
 expectType<2>(Constants.ClientApplicationAssetTypes.BIG);
 
-declare const applicationCommandData: ApplicationCommandData;
+declare const applicationCommandData: Camelize<APIApplicationCommand>;
 declare const applicationCommandResolvable: ApplicationCommandResolvable;
 declare const applicationCommandManager: ApplicationCommandManager;
 {
@@ -805,22 +826,29 @@ declare const applicationCommandManager: ApplicationCommandManager;
   );
 }
 
-declare const applicationNonChoiceOptionData: ApplicationCommandOptionData & {
-  type: CommandOptionNonChoiceResolvableType;
-};
+declare const applicationSubGroupCommandData: Camelize<APIApplicationCommandSubCommandOptions>;
 {
-  // Options aren't allowed on this command type.
-
-  // @ts-expect-error
-  applicationNonChoiceOptionData.choices;
+  expectType<ApplicationCommandOptionType.Subcommand | ApplicationCommandOptionType.SubcommandGroup>(
+    applicationSubGroupCommandData.type,
+  );
+  expectAssignable<APIApplicationCommandOption[] | undefined>(applicationSubGroupCommandData.options);
 }
 
-declare const applicationSubGroupCommandData: ApplicationCommandSubGroupData;
+declare const applicationSubCommandData: ApplicationCommandSubCommandData;
 {
-  expectType<'SUB_COMMAND_GROUP' | ApplicationCommandOptionTypes.SUB_COMMAND_GROUP>(
-    applicationSubGroupCommandData.type,
-  );
-  expectType<ApplicationCommandSubCommandData[] | undefined>(applicationSubGroupCommandData.options);
+  expectType<'SUB_COMMAND' | ApplicationCommandOptionTypes.SUB_COMMAND>(applicationSubCommandData.type);
+
+  // Check that only subcommands can have no subcommand or subcommand group sub-options.
+  expectType<
+    | (
+        | ApplicationCommandChoicesData
+        | ApplicationCommandNonOptionsData
+        | ApplicationCommandChannelOptionData
+        | ApplicationCommandAutocompleteOption
+        | ApplicationCommandNumericOptionData
+      )[]
+    | undefined
+  >(applicationSubCommandData.options);
 }
 
 declare const guildApplicationCommandManager: GuildApplicationCommandManager;