diff --git a/.changeset/migrate-chat-postMessage-to-AJV.md b/.changeset/migrate-chat-postMessage-to-AJV.md
new file mode 100644
index 0000000000000..410c3a60ae5cb
--- /dev/null
+++ b/.changeset/migrate-chat-postMessage-to-AJV.md
@@ -0,0 +1,6 @@
+---
+'@rocket.chat/rest-typings': minor
+'@rocket.chat/meteor': minor
+---
+
+Migrate chat.postMessage endpoint to make it openAPI and AJV compatible
diff --git a/apps/meteor/app/api/server/v1/chat.ts b/apps/meteor/app/api/server/v1/chat.ts
index a00d57e46ae72..e6ea40a474913 100644
--- a/apps/meteor/app/api/server/v1/chat.ts
+++ b/apps/meteor/app/api/server/v1/chat.ts
@@ -1,5 +1,5 @@
 import { Message } from '@rocket.chat/core-services';
-import type { IMessage, IThreadMainMessage } from '@rocket.chat/core-typings';
+import type { IMessage, MessageAttachment, IThreadMainMessage } from '@rocket.chat/core-typings';
 import { MessageTypes } from '@rocket.chat/message-types';
 import { Messages, Users, Rooms, Subscriptions } from '@rocket.chat/models';
 import {
@@ -11,7 +11,6 @@ import {
 	isChatDeleteProps,
 	isChatSyncMessagesProps,
 	isChatGetMessageProps,
-	isChatPostMessageProps,
 	isChatSearchProps,
 	isChatSendMessageProps,
 	isChatIgnoreUserProps,
@@ -119,6 +118,132 @@ const ChatUnfollowMessageLocalSchema = {
 	additionalProperties: false,
 };
 
+//chat.postMessage starts
+type ChatPostMessage =
+	| {
+			roomId: string | string[];
+			text?: string;
+			alias?: string;
+			emoji?: string;
+			avatar?: string;
+			attachments?: MessageAttachment[];
+			customFields?: IMessage['customFields'];
+	  }
+	| {
+			channel: string | string[];
+			text?: string;
+			alias?: string;
+			emoji?: string;
+			avatar?: string;
+			attachments?: MessageAttachment[];
+			customFields?: IMessage['customFields'];
+	  };
+
+const ChatPostMessageSchema = {
+	oneOf: [
+		{
+			type: 'object',
+			properties: {
+				roomId: {
+					oneOf: [
+						{ type: 'string' },
+						{
+							type: 'array',
+							items: {
+								type: 'string',
+							},
+						},
+					],
+				},
+				text: {
+					type: 'string',
+					nullable: true,
+				},
+				alias: {
+					type: 'string',
+					nullable: true,
+				},
+				emoji: {
+					type: 'string',
+					nullable: true,
+				},
+				avatar: {
+					type: 'string',
+					nullable: true,
+				},
+				attachments: {
+					type: 'array',
+					items: {
+						type: 'object',
+					},
+					nullable: true,
+				},
+				tmid: {
+					type: 'string',
+				},
+				customFields: {
+					type: 'object',
+					nullable: true,
+				},
+				parseUrls: {
+					type: 'boolean',
+				},
+			},
+			required: ['roomId'],
+			additionalProperties: false,
+		},
+		{
+			type: 'object',
+			properties: {
+				channel: {
+					oneOf: [
+						{ type: 'string' },
+						{
+							type: 'array',
+							items: {
+								type: 'string',
+							},
+						},
+					],
+				},
+				text: {
+					type: 'string',
+					nullable: true,
+				},
+				alias: {
+					type: 'string',
+					nullable: true,
+				},
+				emoji: {
+					type: 'string',
+					nullable: true,
+				},
+				avatar: {
+					type: 'string',
+					nullable: true,
+				},
+				attachments: {
+					type: 'array',
+					items: {
+						type: 'object',
+					},
+					nullable: true,
+				},
+				customFields: {
+					type: 'object',
+					nullable: true,
+				},
+				parseUrls: {
+					type: 'boolean',
+				},
+			},
+			required: ['channel'],
+			additionalProperties: false,
+		},
+	],
+};
+//chat.postMessage ends
+
 const isChatStarMessageLocalProps = ajv.compile<ChatStarMessageLocal>(ChatStarMessageLocalSchema);
 
 const isChatUnstarMessageLocalProps = ajv.compile<ChatUnstarMessageLocal>(ChatUnstarMessageLocalSchema);
@@ -127,6 +252,8 @@ const isChatFollowMessageLocalProps = ajv.compile<ChatFollowMessageLocal>(ChatFo
 
 const isChatUnfollowMessageLocalProps = ajv.compile<ChatUnfollowMessageLocal>(ChatUnfollowMessageLocalSchema);
 
+const isChatPostMessageLocalProps = ajv.compile<ChatPostMessage>(ChatPostMessageSchema);
+
 API.v1.addRoute(
 	'chat.delete',
 	{ authRequired: true, validateParams: isChatDeleteProps },
@@ -558,13 +685,29 @@ const chatEndpoints = API.v1
 
 			return API.v1.success();
 		},
-	);
-
-API.v1.addRoute(
-	'chat.postMessage',
-	{ authRequired: true, validateParams: isChatPostMessageProps },
-	{
-		async post() {
+	)
+	.post(
+		'chat.postMessage',
+		{
+			authRequired: true,
+			body: isChatPostMessageLocalProps,
+			response: {
+				400: validateBadRequestErrorResponse,
+				401: validateUnauthorizedErrorResponse,
+				200: ajv.compile({
+					type: 'object',
+					properties: {
+						ts: { type: 'number' },
+						channel: { type: 'string' },
+						message: { $ref: '#/components/schemas/IMessage' },
+						success: { type: 'boolean', enum: [true] },
+					},
+					required: ['ts', 'channel', 'message', 'success'],
+					additionalProperties: false,
+				}),
+			},
+		},
+		async function action() {
 			const { text, attachments } = this.bodyParams;
 			const maxAllowedSize = settings.get<number>('Message_MaxAllowedSize') ?? 0;
 
@@ -594,8 +737,7 @@ API.v1.addRoute(
 				message,
 			});
 		},
-	},
-);
+	);
 
 API.v1.addRoute(
 	'chat.search',
diff --git a/packages/rest-typings/src/v1/chat.ts b/packages/rest-typings/src/v1/chat.ts
index b52bba2d61ed5..ae048eda49577 100644
--- a/packages/rest-typings/src/v1/chat.ts
+++ b/packages/rest-typings/src/v1/chat.ts
@@ -739,132 +739,6 @@ const ChatGetDeletedMessagesSchema = {
 
 export const isChatGetDeletedMessagesProps = ajv.compile<ChatGetDeletedMessages>(ChatGetDeletedMessagesSchema);
 
-type ChatPostMessage =
-	| {
-			roomId: string | string[];
-			text?: string;
-			alias?: string;
-			emoji?: string;
-			avatar?: string;
-			attachments?: MessageAttachment[];
-			customFields?: IMessage['customFields'];
-	  }
-	| {
-			channel: string | string[];
-			text?: string;
-			alias?: string;
-			emoji?: string;
-			avatar?: string;
-			attachments?: MessageAttachment[];
-			customFields?: IMessage['customFields'];
-	  };
-
-const ChatPostMessageSchema = {
-	oneOf: [
-		{
-			type: 'object',
-			properties: {
-				roomId: {
-					oneOf: [
-						{ type: 'string' },
-						{
-							type: 'array',
-							items: {
-								type: 'string',
-							},
-						},
-					],
-				},
-				text: {
-					type: 'string',
-					nullable: true,
-				},
-				alias: {
-					type: 'string',
-					nullable: true,
-				},
-				emoji: {
-					type: 'string',
-					nullable: true,
-				},
-				avatar: {
-					type: 'string',
-					nullable: true,
-				},
-				attachments: {
-					type: 'array',
-					items: {
-						type: 'object',
-					},
-					nullable: true,
-				},
-				tmid: {
-					type: 'string',
-				},
-				customFields: {
-					type: 'object',
-					nullable: true,
-				},
-				parseUrls: {
-					type: 'boolean',
-				},
-			},
-			required: ['roomId'],
-			additionalProperties: false,
-		},
-		{
-			type: 'object',
-			properties: {
-				channel: {
-					oneOf: [
-						{ type: 'string' },
-						{
-							type: 'array',
-							items: {
-								type: 'string',
-							},
-						},
-					],
-				},
-				text: {
-					type: 'string',
-					nullable: true,
-				},
-				alias: {
-					type: 'string',
-					nullable: true,
-				},
-				emoji: {
-					type: 'string',
-					nullable: true,
-				},
-				avatar: {
-					type: 'string',
-					nullable: true,
-				},
-				attachments: {
-					type: 'array',
-					items: {
-						type: 'object',
-					},
-					nullable: true,
-				},
-				customFields: {
-					type: 'object',
-					nullable: true,
-				},
-				parseUrls: {
-					type: 'boolean',
-				},
-			},
-			required: ['channel'],
-			additionalProperties: false,
-		},
-	],
-};
-
-export const isChatPostMessageProps = ajv.compile<ChatPostMessage>(ChatPostMessageSchema);
-
 type ChatGetURLPreview = {
 	roomId: IRoom['_id'];
 	url: string;
@@ -982,13 +856,6 @@ export type ChatEndpoints = {
 			};
 		};
 	};
-	'/v1/chat.postMessage': {
-		POST: (params: ChatPostMessage) => {
-			ts: number;
-			channel: IRoom;
-			message: IMessage;
-		};
-	};
 	'/v1/chat.syncThreadMessages': {
 		GET: (params: ChatSyncThreadMessages) => {
 			messages: {