diff --git a/homeassistant/components/mcp/coordinator.py b/homeassistant/components/mcp/coordinator.py
index f3bea5f3d58e..fb099a800530 100644
--- a/homeassistant/components/mcp/coordinator.py
+++ b/homeassistant/components/mcp/coordinator.py
@@ -29,7 +29,6 @@ from homeassistant.exceptions import (
 from homeassistant.helpers import llm
 from homeassistant.helpers.httpx_client import create_async_httpx_client
 from homeassistant.helpers.update_coordinator import DataUpdateCoordinator, UpdateFailed
-from homeassistant.util.json import JsonObjectType
 from homeassistant.util.ssl import SSL_ALPN_HTTP11, SSLCipherList, client_context
 
 from .auth import AuthenticateHeader
@@ -148,7 +147,7 @@ class ModelContextProtocolTool(llm.Tool):
         hass: HomeAssistant,
         tool_input: llm.ToolInput,
         llm_context: llm.LLMContext,
-    ) -> JsonObjectType:
+    ) -> llm.ToolResult:
         """Call the tool."""
         try:
             async with asyncio.timeout(TIMEOUT):
@@ -188,7 +187,10 @@ class ModelContextProtocolTool(llm.Tool):
             raise HomeAssistantError(
                 f"Error communicating with MCP server when calling tool: {error}"
             ) from error
-        return result.model_dump(exclude_unset=True, exclude_none=True)
+        return llm.ToolResult(
+            data=result.model_dump(exclude_unset=True, exclude_none=True),
+            error=bool(result.isError),
+        )
 
 
 class ModelContextProtocolCoordinator(DataUpdateCoordinator[list[llm.Tool]]):
diff --git a/tests/components/mcp/test_init.py b/tests/components/mcp/test_init.py
index a25005da4345..7e903e5066d2 100644
--- a/tests/components/mcp/test_init.py
+++ b/tests/components/mcp/test_init.py
@@ -317,8 +317,42 @@ async def test_llm_get_api_tools(
     }
 
 
+@pytest.mark.parametrize(
+    ("call_tool_result", "expected_result"),
+    [
+        pytest.param(
+            CallToolResult(
+                content=[TextContent(type="text", text="User was born in February")]
+            ),
+            llm.ToolResult(
+                data={
+                    "content": [{"text": "User was born in February", "type": "text"}]
+                }
+            ),
+            id="success",
+        ),
+        pytest.param(
+            CallToolResult(
+                content=[TextContent(type="text", text="Memory search failed")],
+                isError=True,
+            ),
+            llm.ToolResult(
+                data={
+                    "content": [{"text": "Memory search failed", "type": "text"}],
+                    "isError": True,
+                },
+                error=True,
+            ),
+            id="error",
+        ),
+    ],
+)
 async def test_call_tool(
-    hass: HomeAssistant, config_entry: MockConfigEntry, mock_mcp_client: Mock
+    hass: HomeAssistant,
+    config_entry: MockConfigEntry,
+    mock_mcp_client: Mock,
+    call_tool_result: CallToolResult,
+    expected_result: llm.ToolResult,
 ) -> None:
     """Test calling an MCP Tool through the LLM API."""
     mock_mcp_client.return_value.list_tools.return_value = ListToolsResult(
@@ -337,9 +371,7 @@ async def test_call_tool(
     tool = api_instance.tools[0]
     assert tool.name == "search_memory"
 
-    mock_mcp_client.return_value.call_tool.return_value = CallToolResult(
-        content=[TextContent(type="text", text="User was born in February")]
-    )
+    mock_mcp_client.return_value.call_tool.return_value = call_tool_result
     result = await tool.async_call(
         hass,
         llm.ToolInput(
@@ -347,9 +379,7 @@ async def test_call_tool(
         ),
         create_llm_context(),
     )
-    assert result == {
-        "content": [{"text": "User was born in February", "type": "text"}]
-    }
+    assert result == expected_result
 
 
 async def test_call_tool_fails(