diff --git a/mail/components/extensions/schemas/accounts.json b/mail/components/extensions/schemas/accounts.json
index 601da2fa53..824aa25562 100644
--- a/mail/components/extensions/schemas/accounts.json
+++ b/mail/components/extensions/schemas/accounts.json
@@ -88,15 +88,45 @@
       {
         "name": "list",
         "type": "function",
+        "min_manifest_version": 3,
+        "description": "Returns all mail accounts. They will be returned in the same order as used in Thunderbird's folder pane.",
+        "async": "callback",
+        "parameters": [
+          {
+            "name": "includeFolders",
+            "optional": true,
+            "default": false,
+            "type": "boolean",
+            "description": "Specifies whether the returned :ref:`accounts.MailAccount` objects should included their account's folders. Defaults to <value>false</value>."
+          },
+          {
+            "type": "function",
+            "name": "callback",
+            "optional": true,
+            "parameters": [
+              {
+                "type": "array",
+                "items": {
+                  "$ref": "accounts.MailAccount"
+                }
+              }
+            ]
+          }
+        ]
+      },
+      {
+        "name": "list",
+        "type": "function",
+        "max_manifest_version": 2,
         "description": "Returns all mail accounts. They will be returned in the same order as used in Thunderbird's folder pane.",
         "async": "callback",
         "parameters": [
           {
             "name": "includeFolders",
-            "description": "Specifies whether the returned :ref:`accounts.MailAccount` objects should included their account's folders. Defaults to <value>true</value>.",
             "optional": true,
             "default": true,
-            "type": "boolean"
+            "type": "boolean",
+            "description": "Specifies whether the returned :ref:`accounts.MailAccount` objects should included their account's folders. Defaults to <value>true</value>."
           },
           {
             "type": "function",
@@ -116,6 +146,38 @@
       {
         "name": "get",
         "type": "function",
+        "min_manifest_version": 3,
+        "description": "Returns details of the requested account, or <value>null</value> if it doesn't exist.",
+        "async": "callback",
+        "parameters": [
+          {
+            "name": "accountId",
+            "$ref": "MailAccountId"
+          },
+          {
+            "name": "includeFolders",
+            "optional": true,
+            "default": false,
+            "type": "boolean",
+            "description": "Specifies whether the returned :ref:`accounts.MailAccount` object should included the account's folders. Defaults to <value>false</value>."
+          },
+          {
+            "type": "function",
+            "name": "callback",
+            "optional": true,
+            "parameters": [
+              {
+                "$ref": "accounts.MailAccount",
+                "optional": true
+              }
+            ]
+          }
+        ]
+      },
+      {
+        "name": "get",
+        "type": "function",
+        "max_manifest_version": 2,
         "description": "Returns details of the requested account, or <value>null</value> if it doesn't exist.",
         "async": "callback",
         "parameters": [
@@ -125,10 +187,10 @@
           },
           {
             "name": "includeFolders",
-            "description": "Specifies whether the returned :ref:`accounts.MailAccount` object should included the account's folders. Defaults to <value>true</value>.",
             "optional": true,
             "default": true,
-            "type": "boolean"
+            "type": "boolean",
+            "description": "Specifies whether the returned :ref:`accounts.MailAccount` object should included the account's folders. Defaults to <value>true</value>."
           },
           {
             "type": "function",
diff --git a/mail/components/extensions/schemas/addressBook.json b/mail/components/extensions/schemas/addressBook.json
index 1cc8b65296..a888202ae4 100644
--- a/mail/components/extensions/schemas/addressBook.json
+++ b/mail/components/extensions/schemas/addressBook.json
@@ -343,25 +343,25 @@
             "type": "boolean",
             "optional": true,
             "default": true,
-            "description": "Whether to include results from local address books. Defaults to true."
+            "description": "Whether to include results from local address books. Defaults to <value>true</value>."
           },
           "includeRemote": {
             "type": "boolean",
             "optional": true,
             "default": true,
-            "description": "Whether to include results from remote address books. Defaults to true."
+            "description": "Whether to include results from remote address books. Defaults to <value>true</value>."
           },
           "includeReadOnly": {
             "type": "boolean",
             "optional": true,
             "default": true,
-            "description": "Whether to include results from read-only address books. Defaults to true."
+            "description": "Whether to include results from read-only address books. Defaults to <value>true</value>."
           },
           "includeReadWrite": {
             "type": "boolean",
             "optional": true,
             "default": true,
-            "description": "Whether to include results from read-write address books. Defaults to true."
+            "description": "Whether to include results from read-write address books. Defaults to <value>true</value>."
           }
         }
       },
diff --git a/mail/components/extensions/schemas/folders.json b/mail/components/extensions/schemas/folders.json
index 4d31ede94b..fad0420b00 100644
--- a/mail/components/extensions/schemas/folders.json
+++ b/mail/components/extensions/schemas/folders.json
@@ -445,19 +445,50 @@
       {
         "name": "get",
         "type": "function",
+        "min_manifest_version": 3,
         "description": "Returns the specified folder.",
         "async": "callback",
         "parameters": [
           {
-            "name": "folder",
+            "name": "folderId",
             "$ref": "folders.MailFolderId"
           },
           {
             "name": "includeSubFolders",
-            "description": "Specifies whether the returned :ref:`folders.MailFolder` object should include all its nested subfolders . Defaults to <value>true</value>.",
             "optional": true,
+            "type": "boolean",
+            "default": false,
+            "description": "Specifies whether the returned :ref:`folders.MailFolder` object should include all its nested subfolders. Defaults to <value>false</value>."
+          },
+          {
+            "type": "function",
+            "name": "callback",
+            "optional": true,
+            "parameters": [
+              {
+                "$ref": "folders.MailFolder"
+              }
+            ]
+          }
+        ]
+      },
+      {
+        "name": "get",
+        "type": "function",
+        "max_manifest_version": 2,
+        "description": "Returns the specified folder.",
+        "async": "callback",
+        "parameters": [
+          {
+            "name": "folderId",
+            "$ref": "folders.MailFolderId"
+          },
+          {
+            "name": "includeSubFolders",
+            "optional": true,
+            "type": "boolean",
             "default": true,
-            "type": "boolean"
+            "description": "Specifies whether the returned :ref:`folders.MailFolder` object should include all its nested subfolders. Defaults to <value>true</value>."
           },
           {
             "type": "function",
@@ -787,7 +818,7 @@
           },
           {
             "name": "includeSubFolders",
-            "description": "Specifies whether the returned :ref:`folders.MailFolder` object for each parent folder should include its nested subfolders . Defaults to <value>false</value>.",
+            "description": "Specifies whether the returned :ref:`folders.MailFolder` object for each parent folder should include its nested subfolders. Defaults to <value>false</value>.",
             "optional": true,
             "default": false,
             "type": "boolean"
@@ -810,6 +841,40 @@
       {
         "name": "getSubFolders",
         "type": "function",
+        "min_manifest_version": 3,
+        "description": "Get the subfolders of the specified folder or account.",
+        "async": "callback",
+        "parameters": [
+          {
+            "name": "folderId",
+            "$ref": "folders.MailFolderId"
+          },
+          {
+            "name": "includeSubFolders",
+            "optional": true,
+            "type": "boolean",
+            "default": false,
+            "description": "Specifies whether the returned :ref:`folders.MailFolder` object for each direct subfolder should also include all its nested subfolders. Defaults to <value>false</value>."
+          },
+          {
+            "type": "function",
+            "name": "callback",
+            "optional": true,
+            "parameters": [
+              {
+                "type": "array",
+                "items": {
+                  "$ref": "folders.MailFolder"
+                }
+              }
+            ]
+          }
+        ]
+      },
+      {
+        "name": "getSubFolders",
+        "type": "function",
+        "max_manifest_version": 2,
         "description": "Get the subfolders of the specified folder or account.",
         "async": "callback",
         "parameters": [
@@ -820,12 +885,10 @@
                 "$ref": "folders.MailFolderId"
               },
               {
-                "max_manifest_version": 2,
                 "deprecated": "Support deprecated since Thunderbird 121 and removed in Manifest V3: folders.getSubFolders() requires to specify a MailFolderId instead of a full MailFolder object.",
                 "$ref": "folders.MailFolder"
               },
               {
-                "max_manifest_version": 2,
                 "deprecated": "Support deprecated since Thunderbird 121 and removed in Manifest V3: folders.getSubFolders() requires to specify the MailFolderId of the account's rootFolder, instead of a full MailAccount object.",
                 "$ref": "accounts.MailAccount"
               }
@@ -833,10 +896,10 @@
           },
           {
             "name": "includeSubFolders",
-            "description": "Specifies whether the returned :ref:`folders.MailFolder` object for each direct subfolder should also include all its nested subfolders . Defaults to <value>true</value>.",
             "optional": true,
+            "type": "boolean",
             "default": true,
-            "type": "boolean"
+            "description": "Specifies whether the returned :ref:`folders.MailFolder` object for each direct subfolder should also include all its nested subfolders. Defaults to <value>true</value>."
           },
           {
             "type": "function",
diff --git a/mail/components/extensions/test/browser/browser_ext_mailTabs_create.js b/mail/components/extensions/test/browser/browser_ext_mailTabs_create.js
index e2479de663..513865d3c5 100644
--- a/mail/components/extensions/test/browser/browser_ext_mailTabs_create.js
+++ b/mail/components/extensions/test/browser/browser_ext_mailTabs_create.js
@@ -223,7 +223,7 @@ add_task(async function test_create_mv3() {
     }
 
     const [accountId] = await window.waitForMessage();
-    const { rootFolder } = await browser.accounts.get(accountId);
+    const { rootFolder } = await browser.accounts.get(accountId, true);
     const displayedFolder = rootFolder.subFolders[0];
     delete displayedFolder.subFolders;
 
diff --git a/mail/components/extensions/test/browser/browser_ext_mailTabs_mv3.js b/mail/components/extensions/test/browser/browser_ext_mailTabs_mv3.js
index 603125f9cc..6189e23877 100644
--- a/mail/components/extensions/test/browser/browser_ext_mailTabs_mv3.js
+++ b/mail/components/extensions/test/browser/browser_ext_mailTabs_mv3.js
@@ -172,7 +172,7 @@ add_task(async function test_update() {
     }
 
     const [accountId] = await window.waitForMessage();
-    const { rootFolder } = await browser.accounts.get(accountId);
+    const { rootFolder } = await browser.accounts.get(accountId, true);
     const folder = rootFolder.subFolders[0];
 
     await browser.mailTabs.update({ displayedFolderId: folder.id });
diff --git a/mail/components/extensions/test/xpcshell/test_ext_accounts_mv3.js b/mail/components/extensions/test/xpcshell/test_ext_accounts_mv3.js
index f7905683a3..e5c6deb67b 100644
--- a/mail/components/extensions/test/xpcshell/test_ext_accounts_mv3.js
+++ b/mail/components/extensions/test/xpcshell/test_ext_accounts_mv3.js
@@ -22,8 +22,8 @@ add_task(async function test_accounts() {
         "The default account should be null, as none is defined."
       );
 
-      // Check that all folders are included by default.
-      const result1 = await browser.accounts.list();
+      // Check that folders are included on request.
+      const result1 = await browser.accounts.list(true);
       browser.test.assertEq(1, result1.length);
       window.assertDeepEqual(
         {
@@ -63,11 +63,21 @@ add_task(async function test_accounts() {
         );
       }
 
+      // Test that excluding folders works by default.
+      const result1WithOutFoldersDefault = await browser.accounts.list();
+      for (const account of result1WithOutFoldersDefault) {
+        browser.test.assertEq(
+          undefined,
+          account.rootFolder.subFolders,
+          "Folders not included"
+        );
+      }
+
       const [account2Id, account2Name] = await window.sendMessage(
         "create account 2"
       );
       // The new account is defined as default and should be returned first.
-      const result2 = await browser.accounts.list();
+      const result2 = await browser.accounts.list(true);
       browser.test.assertEq(2, result2.length);
       window.assertDeepEqual(
         [
@@ -117,9 +127,9 @@ add_task(async function test_accounts() {
         result2
       );
 
-      const result3 = await browser.accounts.get(account1Id);
+      const result3 = await browser.accounts.get(account1Id, true);
       window.assertDeepEqual(result1[0], result3);
-      const result4 = await browser.accounts.get(account2Id);
+      const result4 = await browser.accounts.get(account2Id, true);
       window.assertDeepEqual(result2[0], result4);
 
       const result3WithoutFolders = await browser.accounts.get(
@@ -141,9 +151,26 @@ add_task(async function test_accounts() {
         "Folders not included"
       );
 
+      const result3WithoutFoldersDefault = await browser.accounts.get(
+        account1Id
+      );
+      browser.test.assertEq(
+        undefined,
+        result3WithoutFoldersDefault.rootFolder.subFolders,
+        "Folders not included"
+      );
+      const result4WithoutFoldersDefault = await browser.accounts.get(
+        account2Id
+      );
+      browser.test.assertEq(
+        undefined,
+        result4WithoutFoldersDefault.rootFolder.subFolders,
+        "Folders not included"
+      );
+
       await window.sendMessage("create folders");
 
-      const result5 = await browser.accounts.get(account1Id);
+      const result5 = await browser.accounts.get(account1Id, true);
       const platformInfo = await browser.runtime.getPlatformInfo();
       window.assertDeepEqual(
         [
@@ -182,7 +209,7 @@ add_task(async function test_accounts() {
         await browser.messages.list(folder.id);
       }
 
-      const result6 = await browser.accounts.get(account2Id);
+      const result6 = await browser.accounts.get(account2Id, true);
       window.assertDeepEqual(
         [
           {
diff --git a/mail/components/extensions/test/xpcshell/test_ext_folders_mv3.js b/mail/components/extensions/test/xpcshell/test_ext_folders_mv3.js
index 81d2253d0c..f79a068961 100644
--- a/mail/components/extensions/test/xpcshell/test_ext_folders_mv3.js
+++ b/mail/components/extensions/test/xpcshell/test_ext_folders_mv3.js
@@ -17,7 +17,7 @@ add_task(
       "background.js": async () => {
         const [accountId, IS_IMAP] = await window.waitForMessage();
 
-        const account = await browser.accounts.get(accountId);
+        const account = await browser.accounts.get(accountId, true);
         const rootFolder = account.rootFolder;
         browser.test.assertEq(3, rootFolder.subFolders.length);
 
@@ -337,7 +337,7 @@ add_task(async function test_FolderInfo_FolderCapabilities_and_favorite() {
         );
       }
 
-      const account = await browser.accounts.get(accountId);
+      const account = await browser.accounts.get(accountId, true);
       const rootFolder = account.rootFolder;
       const folders = await browser.folders.getSubFolders(rootFolder.id, false);
       const InfoTestFolder = folders.find(f => f.name == "InfoTest");
@@ -560,7 +560,7 @@ add_task(
       "background.js": async () => {
         const [accountId] = await window.waitForMessage();
 
-        const account = await browser.accounts.get(accountId);
+        const account = await browser.accounts.get(accountId, true);
         const rootFolder = account.rootFolder;
         const accountFolders = rootFolder.subFolders;
         browser.test.assertEq(
@@ -652,7 +652,7 @@ add_task(
     const files = {
       "background.js": async () => {
         const [accountId] = await window.waitForMessage();
-        const account = await browser.accounts.get(accountId);
+        const account = await browser.accounts.get(accountId, true);
         const rootFolder = account.rootFolder;
 
         // Create a new root folder in the account.
@@ -733,7 +733,14 @@ add_task(
           );
 
           // Check subfolders.
-          testSubFolders(folder.subFolders, expected);
+          browser.test.assertEq(
+            expected.subFolders,
+            !!folder.subFolders,
+            "The folders subFolders should be present as expected."
+          );
+          if (expected.subFolders) {
+            testSubFolders(folder.subFolders, expected);
+          }
 
           // Check parent folders.
           const parents = await browser.folders.getParentFolders(folder.id);
@@ -787,7 +794,7 @@ add_task(
             accountId,
             depth,
             basePath,
-            subFolders: true,
+            subFolders: false,
           });
 
           const subsTrue = await browser.folders.getSubFolders(
@@ -806,7 +813,7 @@ add_task(
             accountId,
             depth,
             basePath,
-            subFolders: true,
+            subFolders: 1, // Only the direct subFolder level is returned.
           });
           testSubFolders(subsFalse, {
             accountId,
diff --git a/mail/components/extensions/test/xpcshell/test_ext_messages_get.js b/mail/components/extensions/test/xpcshell/test_ext_messages_get.js
index a969f9eaf8..cd850a4d02 100644
--- a/mail/components/extensions/test/xpcshell/test_ext_messages_get.js
+++ b/mail/components/extensions/test/xpcshell/test_ext_messages_get.js
@@ -197,7 +197,7 @@ add_task(async function test_plain_mv3() {
 
   const extension = ExtensionTestUtils.loadExtension({
     background: async () => {
-      const accounts = await browser.accounts.list();
+      const accounts = await browser.accounts.list(true);
       browser.test.assertEq(1, accounts.length);
 
       for (const account of accounts) {