diff --git a/astrbot/core/tools/message_tools.py b/astrbot/core/tools/message_tools.py
index ca6f21e9b5..6f44a1647b 100644
--- a/astrbot/core/tools/message_tools.py
+++ b/astrbot/core/tools/message_tools.py
@@ -83,6 +83,7 @@ class SendMessageToUserTool(FunctionTool[AstrAgentContext]):
         "Send message to the user. "
         "Supports various message types including `plain`, `image`, `record`, `video`, `file`, and `mention_user`. "
         "Use this tool to send media files (`image`, `record`, `video`, `file`), "
+        "to reply to a specific earlier message using `reply_to_message_id`, "
         "or when you need to proactively message the user(such as cron job). For other normal text replies, you can output directly and no need to use this tool."
     )
     parameters: dict = Field(
@@ -122,6 +123,15 @@ class SendMessageToUserTool(FunctionTool[AstrAgentContext]):
                         "required": ["type"],
                     },
                 },
+                "reply_to_message_id": {
+                    "type": "string",
+                    "description": (
+                        "Optional platform message ID to quote in the target session, "
+                        "on platforms that support replies. Use only a real message ID "
+                        "from that session, never invent one or use a history database row ID. "
+                        "Omit to send without an explicit quote."
+                    ),
+                },
                 "session": {
                     "type": "string",
                     "description": (
@@ -221,7 +231,18 @@ async def call(
         if not isinstance(messages, list) or not messages:
             return "error: messages parameter is empty or invalid."
 
+        reply_to_message_id = kwargs.get("reply_to_message_id")
+        if reply_to_message_id is not None:
+            if (
+                not isinstance(reply_to_message_id, str)
+                or not reply_to_message_id.strip()
+            ):
+                return "error: reply_to_message_id must be a non-empty string."
+            reply_to_message_id = reply_to_message_id.strip()
+
         components: list[Comp.BaseMessageComponent] = []
+        if reply_to_message_id is not None:
+            components.append(Comp.Reply(id=reply_to_message_id))
         for idx, msg in enumerate(messages):
             if not isinstance(msg, dict):
                 return f"error: messages[{idx}] should be an object."
diff --git a/tests/unit/test_message_tools.py b/tests/unit/test_message_tools.py
index b12a26d8ad..7858d81472 100644
--- a/tests/unit/test_message_tools.py
+++ b/tests/unit/test_message_tools.py
@@ -472,3 +472,74 @@ async def mock_get_booter(*args, **kwargs):
     sent_chain = ctx.context.context.send_message.await_args.args[1]
     sent_file = sent_chain.chain[0]
     assert sent_file.name == "export"
+
+
+@pytest.mark.asyncio
+@pytest.mark.parametrize("session", [None, "test:GroupMessage:other-group"])
+async def test_send_message_quotes_explicit_message_in_target_session(session):
+    """Keep the requested quote before text and mentions in the target session."""
+    from astrbot.core.message.components import At, Plain, Reply
+    from astrbot.core.platform.sources.aiocqhttp.aiocqhttp_message_event import (
+        AiocqhttpMessageEvent,
+    )
+
+    ctx = _make_context(current_session="test:GroupMessage:current-group")
+    result = await SendMessageToUserTool().call(
+        ctx,
+        session=session,
+        reply_to_message_id=" -123456789 ",
+        messages=[
+            {"type": "plain", "text": "About that earlier message"},
+            {"type": "mention_user", "mention_user_id": "42"},
+        ],
+    )
+
+    target, chain = ctx.context.context.send_message.await_args.args
+    assert str(target) == (session or ctx.context.event.unified_msg_origin)
+    assert result.startswith("Message sent")
+    assert [type(comp) for comp in chain.chain] == [Reply, Plain, At]
+    assert chain.chain[0].id == "-123456789"
+    segments = await AiocqhttpMessageEvent._parse_onebot_json(chain)
+    assert segments[0] == {"type": "reply", "data": {"id": "-123456789"}}
+
+
+@pytest.mark.asyncio
+@pytest.mark.parametrize("reply_id", ["", "  ", 123, True, [], {}])
+async def test_send_message_rejects_invalid_reply_id_before_sending(reply_id):
+    """Invalid quote arguments must not send a partial message."""
+    ctx = _make_context()
+    result = await SendMessageToUserTool().call(
+        ctx,
+        reply_to_message_id=reply_id,
+        messages=[{"type": "plain", "text": "hello"}],
+    )
+    assert result == "error: reply_to_message_id must be a non-empty string."
+    ctx.context.context.send_message.assert_not_awaited()
+
+
+@pytest.mark.asyncio
+async def test_send_message_without_reply_id_keeps_plain_chain():
+    """Omitting the quote argument preserves ordinary message sending."""
+    from astrbot.core.message.components import Plain
+
+    ctx = _make_context()
+    await SendMessageToUserTool().call(
+        ctx, messages=[{"type": "plain", "text": "hello"}]
+    )
+    chain = ctx.context.context.send_message.await_args.args[1]
+    assert len(chain.chain) == 1
+    assert isinstance(chain.chain[0], Plain)
+
+
+@pytest.mark.asyncio
+async def test_send_message_reply_does_not_bypass_cross_session_permission():
+    """Quoting a message keeps the existing cross-session permission check."""
+    ctx = _make_context(role="member")
+    result = await SendMessageToUserTool().call(
+        ctx,
+        session="test:GroupMessage:other-group",
+        reply_to_message_id="123",
+        messages=[{"type": "plain", "text": "hello"}],
+    )
+    assert "error" in result.lower()
+    ctx.context.context.send_message.assert_not_awaited()