diff --git a/fastapi_mcp/server.py b/fastapi_mcp/server.py
index 1a7b39e..dfe928c 100644
--- a/fastapi_mcp/server.py
+++ b/fastapi_mcp/server.py
@@ -259,7 +259,7 @@ async def _execute_api_tool(
             # TODO: Better typing for the AsyncClientProtocol. It should return a ResponseProtocol that has a json() method that returns a dict/list/etc.
             try:
                 result = response.json()
-                result_text = json.dumps(result, indent=2)
+                result_text = json.dumps(result, indent=2, ensure_ascii=False)
             except json.JSONDecodeError:
                 if hasattr(response, "text"):
                     result_text = response.text
diff --git a/tests/test_mcp_execute_api_tool.py b/tests/test_mcp_execute_api_tool.py
new file mode 100644
index 0000000..cc05d34
--- /dev/null
+++ b/tests/test_mcp_execute_api_tool.py
@@ -0,0 +1,192 @@
+import pytest
+from unittest.mock import AsyncMock, patch, MagicMock
+from fastapi import FastAPI
+
+from fastapi_mcp import FastApiMCP
+from mcp.types import TextContent
+
+
+@pytest.mark.asyncio
+async def test_execute_api_tool_success(simple_fastapi_app: FastAPI):
+    """Test successful execution of an API tool."""
+    mcp = FastApiMCP(simple_fastapi_app)
+    
+    # Mock the HTTP client response
+    mock_response = MagicMock()
+    mock_response.json.return_value = {"id": 1, "name": "Test Item"}
+    mock_response.status_code = 200
+    mock_response.text = '{"id": 1, "name": "Test Item"}'
+    
+    # Mock the HTTP client
+    mock_client = AsyncMock()
+    mock_client.get.return_value = mock_response
+    
+    # Test parameters
+    tool_name = "get_item"
+    arguments = {"item_id": 1}
+    
+    # Execute the tool
+    with patch.object(mcp, '_http_client', mock_client):
+        result = await mcp._execute_api_tool(
+            client=mock_client,
+            tool_name=tool_name,
+            arguments=arguments,
+            operation_map=mcp.operation_map
+        )
+    
+    # Verify the result
+    assert len(result) == 1
+    assert isinstance(result[0], TextContent)
+    assert result[0].text == '{\n  "id": 1,\n  "name": "Test Item"\n}'
+    
+    # Verify the HTTP client was called correctly
+    mock_client.get.assert_called_once_with(
+        "/items/1",
+        params={},
+        headers={}
+    )
+
+
+@pytest.mark.asyncio
+async def test_execute_api_tool_with_query_params(simple_fastapi_app: FastAPI):
+    """Test execution of an API tool with query parameters."""
+    mcp = FastApiMCP(simple_fastapi_app)
+    
+    # Mock the HTTP client response
+    mock_response = MagicMock()
+    mock_response.json.return_value = [{"id": 1, "name": "Item 1"}, {"id": 2, "name": "Item 2"}]
+    mock_response.status_code = 200
+    mock_response.text = '[{"id": 1, "name": "Item 1"}, {"id": 2, "name": "Item 2"}]'
+    
+    # Mock the HTTP client
+    mock_client = AsyncMock()
+    mock_client.get.return_value = mock_response
+    
+    # Test parameters
+    tool_name = "list_items"
+    arguments = {"skip": 0, "limit": 2}
+    
+    # Execute the tool
+    with patch.object(mcp, '_http_client', mock_client):
+        result = await mcp._execute_api_tool(
+            client=mock_client,
+            tool_name=tool_name,
+            arguments=arguments,
+            operation_map=mcp.operation_map
+        )
+    
+    # Verify the result
+    assert len(result) == 1
+    assert isinstance(result[0], TextContent)
+    
+    # Verify the HTTP client was called with query parameters
+    mock_client.get.assert_called_once_with(
+        "/items/",
+        params={"skip": 0, "limit": 2},
+        headers={}
+    )
+
+
+@pytest.mark.asyncio
+async def test_execute_api_tool_with_body(simple_fastapi_app: FastAPI):
+    """Test execution of an API tool with request body."""
+    mcp = FastApiMCP(simple_fastapi_app)
+    
+    # Mock the HTTP client response
+    mock_response = MagicMock()
+    mock_response.json.return_value = {"id": 1, "name": "New Item"}
+    mock_response.status_code = 200
+    mock_response.text = '{"id": 1, "name": "New Item"}'
+    
+    # Mock the HTTP client
+    mock_client = AsyncMock()
+    mock_client.post.return_value = mock_response
+    
+    # Test parameters
+    tool_name = "create_item"
+    arguments = {
+        "item": {
+            "id": 1,
+            "name": "New Item",
+            "price": 10.0,
+            "tags": ["tag1"],
+            "description": "New item description"
+        }
+    }
+    
+    # Execute the tool
+    with patch.object(mcp, '_http_client', mock_client):
+        result = await mcp._execute_api_tool(
+            client=mock_client,
+            tool_name=tool_name,
+            arguments=arguments,
+            operation_map=mcp.operation_map
+        )
+    
+    # Verify the result
+    assert len(result) == 1
+    assert isinstance(result[0], TextContent)
+    
+    # Verify the HTTP client was called with the request body
+    mock_client.post.assert_called_once_with(
+        "/items/",
+        params={},
+        headers={},
+        json=arguments
+    )
+
+
+@pytest.mark.asyncio
+async def test_execute_api_tool_with_non_ascii_chars(simple_fastapi_app: FastAPI):
+    """Test execution of an API tool with non-ASCII characters."""
+    mcp = FastApiMCP(simple_fastapi_app)
+    
+    # Test data with both ASCII and non-ASCII characters
+    test_data = {
+        "id": 1,
+        "name": "你好 World",  # Chinese characters + ASCII
+        "price": 10.0,
+        "tags": ["tag1", "标签2"],  # Chinese characters in tags
+        "description": "这是一个测试描述"  # All Chinese characters
+    }
+    
+    # Mock the HTTP client response
+    mock_response = MagicMock()
+    mock_response.json.return_value = test_data
+    mock_response.status_code = 200
+    mock_response.text = '{"id": 1, "name": "你好 World", "price": 10.0, "tags": ["tag1", "标签2"], "description": "这是一个测试描述"}'
+    
+    # Mock the HTTP client
+    mock_client = AsyncMock()
+    mock_client.get.return_value = mock_response
+    
+    # Test parameters
+    tool_name = "get_item"
+    arguments = {"item_id": 1}
+    
+    # Execute the tool
+    with patch.object(mcp, '_http_client', mock_client):
+        result = await mcp._execute_api_tool(
+            client=mock_client,
+            tool_name=tool_name,
+            arguments=arguments,
+            operation_map=mcp.operation_map
+        )
+    
+    # Verify the result
+    assert len(result) == 1
+    assert isinstance(result[0], TextContent)
+    
+    # Verify that the response contains both ASCII and non-ASCII characters
+    response_text = result[0].text
+    assert "你好" in response_text  # Chinese characters preserved
+    assert "World" in response_text  # ASCII characters preserved
+    assert "标签2" in response_text  # Chinese characters in tags preserved
+    assert "这是一个测试描述" in response_text  # All Chinese description preserved
+    
+    # Verify the HTTP client was called correctly
+    mock_client.get.assert_called_once_with(
+        "/items/1",
+        params={},
+        headers={}
+    )