diff --git a/packages/longbridge-tools/src/errors.ts b/packages/longbridge-tools/src/errors.ts
index 1e8d83b..d2f7d59 100644
--- a/packages/longbridge-tools/src/errors.ts
+++ b/packages/longbridge-tools/src/errors.ts
@@ -4,6 +4,7 @@ export type ErrorCode =
   | 'LONGBRIDGE_RATE_LIMITED'
   | 'LONGBRIDGE_TIMEOUT'
   | 'INVALID_SYMBOL'
+  | 'INVALID_ARGUMENT'
   | 'LONGBRIDGE_PARSE_FAILURE'
   | 'LONGBRIDGE_UNKNOWN';
 
diff --git a/packages/longbridge-tools/src/phase-two.test.ts b/packages/longbridge-tools/src/phase-two.test.ts
index a9019d0..825683f 100644
--- a/packages/longbridge-tools/src/phase-two.test.ts
+++ b/packages/longbridge-tools/src/phase-two.test.ts
@@ -294,4 +294,31 @@ describe('phase-2 error handling', () => {
       /parse depth response/
     );
   });
+
+  it('rejects invalid calendar symbols before invoking the CLI', async () => {
+    await expect(
+      getCalendarEvents({ eventType: 'dividend', symbols: ['NVDA.US', 'not-a-symbol'] })
+    ).rejects.toMatchObject({ code: 'INVALID_SYMBOL' });
+    expect(execaMock).not.toHaveBeenCalled();
+  });
+
+  it('rejects calendar dates that are not YYYY-MM-DD', async () => {
+    await expect(
+      getCalendarEvents({ eventType: 'dividend', start: '--symbol' })
+    ).rejects.toMatchObject({ code: 'INVALID_ARGUMENT' });
+    await expect(
+      getCalendarEvents({ eventType: 'dividend', end: '2026/01/01' })
+    ).rejects.toMatchObject({ code: 'INVALID_ARGUMENT' });
+    expect(execaMock).not.toHaveBeenCalled();
+  });
+
+  it('rejects a non-positive or non-integer calendar count', async () => {
+    await expect(
+      getCalendarEvents({ eventType: 'dividend', count: -1 })
+    ).rejects.toMatchObject({ code: 'INVALID_ARGUMENT' });
+    await expect(
+      getCalendarEvents({ eventType: 'dividend', count: 1.5 })
+    ).rejects.toMatchObject({ code: 'INVALID_ARGUMENT' });
+    expect(execaMock).not.toHaveBeenCalled();
+  });
 });
diff --git a/packages/longbridge-tools/src/tools/calendar.ts b/packages/longbridge-tools/src/tools/calendar.ts
index eaf6176..71f38d6 100644
--- a/packages/longbridge-tools/src/tools/calendar.ts
+++ b/packages/longbridge-tools/src/tools/calendar.ts
@@ -1,5 +1,7 @@
 import { executeLongBridge } from '../executor.ts';
 import { parseCalendarResponse } from '../parser.ts';
+import { LongBridgeError } from '../errors.ts';
+import { validateSymbolOrThrow } from '../validator.ts';
 import type { CalendarEvent } from '../types.ts';
 
 export type CalendarEventType =
@@ -23,10 +25,30 @@ export interface GetCalendarEventsOptions {
   count?: number;
 }
 
+const DATE_REGEX = /^\d{4}-\d{2}-\d{2}$/;
+
 /** Upcoming finance-calendar events of a given type. */
 export async function getCalendarEvents(
   options: GetCalendarEventsOptions
 ): Promise<CalendarEvent[]> {
+  for (const symbol of options.symbols ?? []) {
+    validateSymbolOrThrow(symbol);
+  }
+  for (const [name, value] of [['start', options.start], ['end', options.end]] as const) {
+    if (value !== undefined && !DATE_REGEX.test(value)) {
+      throw new LongBridgeError(
+        `INVALID_ARGUMENT: ${name} must be YYYY-MM-DD, got "${value}"`,
+        'INVALID_ARGUMENT'
+      );
+    }
+  }
+  if (options.count !== undefined && (!Number.isInteger(options.count) || options.count < 1)) {
+    throw new LongBridgeError(
+      `INVALID_ARGUMENT: count must be a positive integer, got ${options.count}`,
+      'INVALID_ARGUMENT'
+    );
+  }
+
   const args = ['finance-calendar', options.eventType];
   for (const symbol of options.symbols ?? []) {
     args.push('--symbol', symbol);