diff --git a/app/api/endpoints/mcp.py b/app/api/endpoints/mcp.py
index f3f342daa..7e7daae0f 100644
--- a/app/api/endpoints/mcp.py
+++ b/app/api/endpoints/mcp.py
@@ -109,13 +109,14 @@ def create_jsonrpc_error(
     """
     创建 JSON-RPC 错误响应
     """
+    error_detail: Dict[str, object] = {"code": code, "message": message}
     error = {
         "jsonrpc": "2.0",
         "id": request_id,
-        "error": {"code": code, "message": message},
+        "error": error_detail,
     }
     if data is not None:
-        error["error"]["data"] = data
+        error_detail["data"] = data
     return error
 
 
@@ -164,7 +165,7 @@ async def _dispatch_jsonrpc_method(
     },
 )
 async def mcp_jsonrpc(
-    request: Request, _: Annotated[str, Depends(verify_apikey)] = None
+    request: Request, _: Annotated[Union[str, None], Depends(verify_apikey)] = None
 ) -> Union[JSONResponse, Response]:
     """
     MCP 标准 JSON-RPC 2.0 端点
@@ -184,7 +185,9 @@ async def mcp_jsonrpc(
     if not isinstance(body, dict) or body.get("jsonrpc") != "2.0":
         return JSONResponse(
             status_code=400,
-            content=create_jsonrpc_error(body.get("id"), -32600, "Invalid Request"),
+            content=create_jsonrpc_error(
+                body.get("id") if isinstance(body, dict) else None, -32600, "Invalid Request"
+            ),
         )
 
     method = body.get("method")
@@ -300,7 +303,7 @@ async def handle_tools_call(params: Dict[str, Any]) -> Dict[str, Any]:
     },
 )
 async def delete_mcp_session(
-    _: Annotated[str, Depends(verify_apikey)] = None,
+    _: Annotated[Union[str, None], Depends(verify_apikey)] = None,
 ) -> Union[JSONResponse, Response]:
     """
     终止 MCP 会话（无状态模式下仅返回成功）
@@ -347,7 +350,7 @@ async def list_tools(_: Annotated[str, Depends(verify_apikey)], page: Compatible
     summary="调用工具",
     response_model=_SchemaResponse[_SchemaToolCallData],
 )
-async def call_tool(request: _SchemaToolCallRequest, _: Annotated[str, Depends(verify_apikey)] = None) -> Any:
+async def call_tool(request: _SchemaToolCallRequest, _: Annotated[Union[str, None], Depends(verify_apikey)] = None) -> Any:
     """
     调用指定的工具
 
diff --git a/docs/mcp-api.md b/docs/mcp-api.md
index da4508260..d6e108be5 100644
--- a/docs/mcp-api.md
+++ b/docs/mcp-api.md
@@ -51,6 +51,10 @@ Fake-IP 等非公网解析地址需要通过 `IMAGE_PROXY_ALLOWED_PRIVATE_RANGES
 ### 端点
 **POST** `/api/v1/mcp`
 
+请求体须为单个 JSON-RPC 2.0 对象。非对象值（包括数组批量请求）或错误的协议版本返回
+HTTP 400、JSON-RPC 错误码 `-32600`；非对象请求的 `id` 为 `null`。无法解析的 JSON 返回
+HTTP 400、错误码 `-32700`。
+
 ### 支持的方法
 - `initialize`: 初始化会话，协商协议版本和能力。
 - `notifications/initialized`: 客户端确认初始化完成。
diff --git a/tests/test_mcp_requests.py b/tests/test_mcp_requests.py
new file mode 100644
index 000000000..a7beffc57
--- /dev/null
+++ b/tests/test_mcp_requests.py
@@ -0,0 +1,43 @@
+"""MCP JSON-RPC 请求格式错误的协议回归。"""
+
+import json
+
+import pytest
+from fastapi import FastAPI
+from fastapi.testclient import TestClient
+
+from app.api.endpoints import mcp
+
+
+@pytest.mark.parametrize(
+    ("body", "request_id"),
+    [
+        (None, None),
+        ([], None),
+        ([{"jsonrpc": "2.0", "method": "ping", "id": 1}], None),
+        ("invalid", None),
+        (1, None),
+        (True, None),
+        ({}, None),
+        ({"jsonrpc": "1.0", "id": 7}, 7),
+    ],
+)
+def test_invalid_request_returns_jsonrpc_error(body: object, request_id: object) -> None:
+    """非对象及错误版本的请求须返回 400 协议错误，不能在取 id 时崩溃。"""
+    app = FastAPI()
+    app.include_router(mcp.router, prefix="/mcp")
+    app.dependency_overrides[mcp.verify_apikey] = lambda: "test-api-key"
+
+    with TestClient(app) as client:
+        response = client.post(
+            "/mcp",
+            content=json.dumps(body),
+            headers={"Content-Type": "application/json"},
+        )
+
+    assert response.status_code == 400
+    assert response.json() == {
+        "jsonrpc": "2.0",
+        "id": request_id,
+        "error": {"code": -32600, "message": "Invalid Request"},
+    }