diff --git a/package-lock.json b/package-lock.json
index 698e4fc..d558220 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -11,7 +11,7 @@
       "dependencies": {
         "@modelcontextprotocol/sdk": "^1.25.3",
         "decimal.js": "^10.4.3",
-        "ynab": "^1.35.0",
+        "ynab": "^2.10.0",
         "zod": "^3.23.8"
       },
       "bin": {
@@ -5212,15 +5212,15 @@
       "license": "ISC"
     },
     "node_modules/ynab": {
-      "version": "1.55.0",
-      "resolved": "https://registry.npmjs.org/ynab/-/ynab-1.55.0.tgz",
-      "integrity": "sha512-i5MEPWpMILUiqQ9JXFBa//ljGEAtVziyx2C1s09THWoPu8b1R7k/NjDQRsM3YpYUDFTDyKRTmKOA+vxzkkK9dQ==",
+      "version": "2.10.0",
+      "resolved": "https://registry.npmjs.org/ynab/-/ynab-2.10.0.tgz",
+      "integrity": "sha512-zDH++4mbFpVDbDW1qIYS3pG3sPVtdth7c45aEfU7pVNqIcK6aVzK8eSksyOarrzaPKSq4OA9AXq1ixC7WGdpow==",
       "license": "Apache-2.0",
       "dependencies": {
         "fetch-ponyfill": "^7.1.0"
       },
       "engines": {
-        "node": "<=18"
+        "node": ">=14"
       }
     },
     "node_modules/yocto-queue": {
diff --git a/package.json b/package.json
index 0104257..6a17aaf 100644
--- a/package.json
+++ b/package.json
@@ -39,7 +39,7 @@
   "dependencies": {
     "@modelcontextprotocol/sdk": "^1.25.3",
     "decimal.js": "^10.4.3",
-    "ynab": "^1.35.0",
+    "ynab": "^2.10.0",
     "zod": "^3.23.8"
   },
   "devDependencies": {
diff --git a/src/tools/budgets/get-budget-settings.ts b/src/tools/budgets/get-budget-settings.ts
index 61411f7..a53e1e1 100644
--- a/src/tools/budgets/get-budget-settings.ts
+++ b/src/tools/budgets/get-budget-settings.ts
@@ -43,6 +43,14 @@ Returns currency format, date format, and currency ISO code.`,
 // Handler function
 /**
  * Handler for the ynab_get_budget_settings tool.
+ *
+ * @param args - Tool arguments containing optional budget_id
+ * @param client - YNAB client instance for API calls
+ * @returns JSON string with budget settings including date_format and currency_format
+ *
+ * @remarks
+ * SDK v2 made date_format and currency_format nullable. This handler returns null
+ * for missing formats rather than empty strings to preserve semantic meaning.
  */
 export async function handleGetBudgetSettings(
   args: Record<string, unknown>,
@@ -54,21 +62,26 @@ export async function handleGetBudgetSettings(
   const response = await client.getBudgetSettingsById(budgetId);
   const settings = response.data.settings;
 
+  const dateFormat = settings.date_format;
+  const currencyFormat = settings.currency_format;
+
   return JSON.stringify(
     {
       budget_id: sanitizeString(budgetId) ?? '',
       settings: {
-        date_format: sanitizeString(settings.date_format.format) ?? '',
-        currency_format: {
-          iso_code: sanitizeString(settings.currency_format.iso_code) ?? '',
-          example_format: sanitizeString(settings.currency_format.example_format) ?? '',
-          decimal_digits: settings.currency_format.decimal_digits,
-          decimal_separator: sanitizeString(settings.currency_format.decimal_separator) ?? '',
-          symbol_first: settings.currency_format.symbol_first,
-          group_separator: sanitizeString(settings.currency_format.group_separator) ?? '',
-          currency_symbol: sanitizeString(settings.currency_format.currency_symbol) ?? '',
-          display_symbol: settings.currency_format.display_symbol,
-        },
+        date_format: dateFormat?.format ? sanitizeString(dateFormat.format) : null,
+        currency_format: currencyFormat
+          ? {
+              iso_code: sanitizeString(currencyFormat.iso_code) ?? '',
+              example_format: sanitizeString(currencyFormat.example_format) ?? '',
+              decimal_digits: currencyFormat.decimal_digits,
+              decimal_separator: sanitizeString(currencyFormat.decimal_separator) ?? '',
+              symbol_first: currencyFormat.symbol_first,
+              group_separator: sanitizeString(currencyFormat.group_separator) ?? '',
+              currency_symbol: sanitizeString(currencyFormat.currency_symbol) ?? '',
+              display_symbol: currencyFormat.display_symbol,
+            }
+          : null,
       },
     },
     null,
diff --git a/src/tools/transactions/create-transaction.ts b/src/tools/transactions/create-transaction.ts
index 4e46007..b92a8a3 100644
--- a/src/tools/transactions/create-transaction.ts
+++ b/src/tools/transactions/create-transaction.ts
@@ -122,6 +122,16 @@ Amount should be negative for expenses/outflows and positive for income/inflows.
 // Handler function
 /**
  * Handler for the ynab_create_transaction tool.
+ *
+ * @param args - Tool arguments including account_id, date, amount, and optional fields
+ * @param client - YNAB client instance for API calls
+ * @returns JSON string with created transaction details
+ * @throws Error if transaction creation fails
+ *
+ * @remarks
+ * Uses ynab.NewTransaction type (SDK v2) for creating transactions.
+ * Enum types are cast to ynab.TransactionClearedStatus and ynab.TransactionFlagColor.
+ * Security checks (rate limiting, write permission, audit logging) are handled by YnabClient.
  */
 export async function handleCreateTransaction(
   args: Record<string, unknown>,
@@ -131,7 +141,7 @@ export async function handleCreateTransaction(
   const budgetId = client.resolveBudgetId(validated.budget_id);
 
   // Build transaction data, only including defined fields
-  const transactionData: ynab.SaveTransaction = {
+  const transactionData: ynab.NewTransaction = {
     account_id: validated.account_id,
     date: validated.date,
     amount: toMilliunits(validated.amount),
@@ -142,10 +152,10 @@ export async function handleCreateTransaction(
   if (validated.category_id !== undefined) transactionData.category_id = validated.category_id;
   if (validated.memo !== undefined) transactionData.memo = validated.memo;
   if (validated.cleared !== undefined)
-    transactionData.cleared = validated.cleared as unknown as ynab.SaveTransaction.ClearedEnum;
+    transactionData.cleared = validated.cleared as ynab.TransactionClearedStatus;
   if (validated.approved !== undefined) transactionData.approved = validated.approved;
   if (validated.flag_color !== undefined)
-    transactionData.flag_color = validated.flag_color as unknown as ynab.SaveTransaction.FlagColorEnum;
+    transactionData.flag_color = validated.flag_color as ynab.TransactionFlagColor;
 
   const response = await client.createTransaction(budgetId, {
     transaction: transactionData,
diff --git a/src/tools/transactions/create-transactions.ts b/src/tools/transactions/create-transactions.ts
index 8f9ee7e..e9c756f 100644
--- a/src/tools/transactions/create-transactions.ts
+++ b/src/tools/transactions/create-transactions.ts
@@ -96,6 +96,15 @@ Use import_id to prevent duplicate imports.`,
 // Handler function
 /**
  * Handler for the ynab_create_transactions tool.
+ *
+ * @param args - Tool arguments including transactions array (max 100)
+ * @param client - YNAB client instance for API calls
+ * @returns JSON string with created transactions and duplicate info
+ *
+ * @remarks
+ * Uses ynab.NewTransaction type (SDK v2) for bulk transaction creation.
+ * Enum types are cast to ynab.TransactionClearedStatus and ynab.TransactionFlagColor.
+ * Security checks (rate limiting, write permission, audit logging) are handled by YnabClient.
  */
 export async function handleCreateTransactions(
   args: Record<string, unknown>,
@@ -105,8 +114,8 @@ export async function handleCreateTransactions(
   const budgetId = client.resolveBudgetId(validated.budget_id);
 
   // Convert transactions to YNAB format
-  const ynabTransactions: ynab.SaveTransaction[] = validated.transactions.map((t) => {
-    const txn: ynab.SaveTransaction = {
+  const ynabTransactions: ynab.NewTransaction[] = validated.transactions.map((t) => {
+    const txn: ynab.NewTransaction = {
       account_id: t.account_id,
       date: t.date,
       amount: toMilliunits(t.amount),
@@ -116,10 +125,10 @@ export async function handleCreateTransactions(
     if (t.payee_name !== undefined) txn.payee_name = t.payee_name;
     if (t.category_id !== undefined) txn.category_id = t.category_id;
     if (t.memo !== undefined) txn.memo = t.memo;
-    if (t.cleared !== undefined) txn.cleared = t.cleared as unknown as ynab.SaveTransaction.ClearedEnum;
+    if (t.cleared !== undefined) txn.cleared = t.cleared as ynab.TransactionClearedStatus;
     if (t.approved !== undefined) txn.approved = t.approved;
     if (t.flag_color !== undefined)
-      txn.flag_color = t.flag_color as unknown as ynab.SaveTransaction.FlagColorEnum;
+      txn.flag_color = t.flag_color as ynab.TransactionFlagColor;
     if (t.import_id !== undefined) txn.import_id = t.import_id;
 
     return txn;
diff --git a/src/tools/transactions/update-transaction.ts b/src/tools/transactions/update-transaction.ts
index 76ff4b3..d1e61a4 100644
--- a/src/tools/transactions/update-transaction.ts
+++ b/src/tools/transactions/update-transaction.ts
@@ -136,6 +136,15 @@ Only provide the fields you want to change.`,
 // Handler function
 /**
  * Handler for the ynab_update_transaction tool.
+ *
+ * @param args - Tool arguments including transaction_id and fields to update
+ * @param client - YNAB client instance for API calls
+ * @returns JSON string with updated transaction details
+ *
+ * @remarks
+ * Uses ynab.SaveTransactionWithOptionalFields type (SDK v2) for partial updates.
+ * Enum types are cast to ynab.TransactionClearedStatus and ynab.TransactionFlagColor.
+ * Security checks (rate limiting, write permission, audit logging) are handled by YnabClient.
  */
 export async function handleUpdateTransaction(
   args: Record<string, unknown>,
@@ -155,12 +164,10 @@ export async function handleUpdateTransaction(
   if (validated.category_id !== undefined) updateData.category_id = validated.category_id;
   if (validated.memo !== undefined) updateData.memo = validated.memo;
   if (validated.cleared !== undefined)
-    updateData.cleared =
-      validated.cleared as unknown as ynab.SaveTransactionWithOptionalFields.ClearedEnum;
+    updateData.cleared = validated.cleared as ynab.TransactionClearedStatus;
   if (validated.approved !== undefined) updateData.approved = validated.approved;
   if (validated.flag_color !== undefined)
-    updateData.flag_color =
-      validated.flag_color as unknown as ynab.SaveTransactionWithOptionalFields.FlagColorEnum | null;
+    updateData.flag_color = validated.flag_color as ynab.TransactionFlagColor | null;
 
   const response = await client.updateTransaction(budgetId, validated.transaction_id, {
     transaction: updateData,