fix(tools): forward custom name and description from VertexAiSearchTool bypass path to DiscoveryEngineSearchTool

src/google/adk/agents/llm_agent.py

@@ -178,6 +178,8 @@ async def _convert_tool_union_to_tools(
               search_engine_id=vais_tool.search_engine_id,
               filter=vais_tool.filter,
               max_results=vais_tool.max_results,
+              name=vais_tool._bypass_tool_name,
+              description=vais_tool._bypass_tool_description,
           )
       ]
   from ..workflow._base_node import BaseNode

src/google/adk/tools/discovery_engine_search_tool.py

@@ -144,6 +144,8 @@ def __init__(
       *,
       search_result_mode: Optional[SearchResultMode] = None,
       location: Optional[str] = None,
+      name: Optional[str] = None,
+      description: Optional[str] = None,
   ):
     """Initializes the DiscoveryEngineSearchTool.
 
@@ -164,8 +166,16 @@ def __init__(
       location: Optional endpoint location override.
         Examples: "global", "us", "eu". If not specified, location is inferred
           from `data_store_id` or `search_engine_id` and defaults to "global".
+      name: Optional custom name for the tool. Defaults to
+        "discovery_engine_search".
+      description: Optional custom description for the tool. Defaults to
+        the docstring of discovery_engine_search.
     """
     super().__init__(self.discovery_engine_search)
+    if name:
+      self.name = name
+    if description:
+      self.description = description
     if (data_store_id is None and search_engine_id is None) or (
         data_store_id is not None and search_engine_id is not None
     ):

src/google/adk/tools/vertex_ai_search_tool.py

@@ -71,6 +71,8 @@ def __init__(
       filter: Optional[str] = None,
       max_results: Optional[int] = None,
       bypass_multi_tools_limit: bool = False,
+      name: Optional[str] = None,
+      description: Optional[str] = None,
   ):
     """Initializes the Vertex AI Search tool.
 
@@ -86,6 +88,19 @@ def __init__(
       max_results: The maximum number of results to return.
       bypass_multi_tools_limit: Whether to bypass the multi tools limitation,
         so that the tool can be used with other tools in the same agent.
+      name: Optional custom name for the tool. Only used when
+        ``bypass_multi_tools_limit=True``, in which case the tool is converted
+        to a client-side :class:`DiscoveryEngineSearchTool`. When ``None``
+        (default) the converted tool is named ``discovery_engine_search``.
+        Has no effect when ``bypass_multi_tools_limit=False`` because the
+        built-in grounding path does not expose a callable tool name to the
+        model. Providing a domain-specific name (e.g.
+        ``"knowledge_base_search"``) prevents prompt-fragility issues where
+        lightweight models guess generic names like ``search`` and trigger a
+        ``ValueError: Tool 'search' not found`` at runtime.
+      description: Optional custom description for the tool. Only used when
+        ``bypass_multi_tools_limit=True``. When ``None`` (default) the
+        converted tool uses the docstring of its internal search function.
 
     Raises:
       ValueError: If both data_store_id and search_engine_id are not specified
@@ -109,6 +124,9 @@ def __init__(
     self.filter = filter
     self.max_results = max_results
     self.bypass_multi_tools_limit = bypass_multi_tools_limit
+    # Stored separately so they never shadow the built-in grounding name.
+    self._bypass_tool_name = name
+    self._bypass_tool_description = description
 
   def _build_vertex_ai_search_config(
       self, readonly_context: ReadonlyContext

tests/unittests/agents/test_llm_agent_fields.py

@@ -723,6 +723,135 @@ async def test_handle_vais_in_hierarchy_no_bypass(self):
     assert tools[0].name == 'vertex_ai_search'
     assert tools[0].__class__.__name__ == 'VertexAiSearchTool'
 
+  @mock.patch(
+      'google.auth.default',
+      mock.MagicMock(return_value=('credentials', 'project')),
+  )
+  async def test_vais_bypass_custom_name_forwarded(self):
+    """Custom name on VertexAiSearchTool is forwarded to DiscoveryEngineSearchTool."""
+    agent = LlmAgent(
+        name='test_agent',
+        model='gemini-pro',
+        tools=[
+            self._my_tool,
+            VertexAiSearchTool(
+                data_store_id='test_data_store_id',
+                bypass_multi_tools_limit=True,
+                name='knowledge_base_search',
+            ),
+        ],
+    )
+    ctx = await _create_readonly_context(agent)
+    tools = await agent.canonical_tools(ctx)
+
+    assert len(tools) == 2
+    assert tools[1].name == 'knowledge_base_search'
+    assert tools[1].__class__.__name__ == 'DiscoveryEngineSearchTool'
+
+  @mock.patch(
+      'google.auth.default',
+      mock.MagicMock(return_value=('credentials', 'project')),
+  )
+  async def test_vais_bypass_custom_description_forwarded(self):
+    """Custom description on VertexAiSearchTool is forwarded to DiscoveryEngineSearchTool."""
+    custom_desc = 'Search the internal knowledge base for product information.'
+    agent = LlmAgent(
+        name='test_agent',
+        model='gemini-pro',
+        tools=[
+            self._my_tool,
+            VertexAiSearchTool(
+                data_store_id='test_data_store_id',
+                bypass_multi_tools_limit=True,
+                description=custom_desc,
+            ),
+        ],
+    )
+    ctx = await _create_readonly_context(agent)
+    tools = await agent.canonical_tools(ctx)
+
+    assert len(tools) == 2
+    assert tools[1].description == custom_desc
+    assert tools[1].__class__.__name__ == 'DiscoveryEngineSearchTool'
+
+  @mock.patch(
+      'google.auth.default',
+      mock.MagicMock(return_value=('credentials', 'project')),
+  )
+  async def test_vais_bypass_custom_name_and_description_forwarded(self):
+    """Both custom name and description are forwarded to DiscoveryEngineSearchTool."""
+    custom_name = 'product_search'
+    custom_desc = 'Search the product catalogue.'
+    agent = LlmAgent(
+        name='test_agent',
+        model='gemini-pro',
+        tools=[
+            self._my_tool,
+            VertexAiSearchTool(
+                data_store_id='test_data_store_id',
+                bypass_multi_tools_limit=True,
+                name=custom_name,
+                description=custom_desc,
+            ),
+        ],
+    )
+    ctx = await _create_readonly_context(agent)
+    tools = await agent.canonical_tools(ctx)
+
+    assert len(tools) == 2
+    assert tools[1].name == custom_name
+    assert tools[1].description == custom_desc
+    assert tools[1].__class__.__name__ == 'DiscoveryEngineSearchTool'
+
+  @mock.patch(
+      'google.auth.default',
+      mock.MagicMock(return_value=('credentials', 'project')),
+  )
+  async def test_vais_bypass_default_name_unchanged_when_no_custom_name(self):
+    """Default name is still 'discovery_engine_search' when no custom name provided."""
+    agent = LlmAgent(
+        name='test_agent',
+        model='gemini-pro',
+        tools=[
+            self._my_tool,
+            VertexAiSearchTool(
+                data_store_id='test_data_store_id',
+                bypass_multi_tools_limit=True,
+            ),
+        ],
+    )
+    ctx = await _create_readonly_context(agent)
+    tools = await agent.canonical_tools(ctx)
+
+    assert len(tools) == 2
+    assert tools[1].name == 'discovery_engine_search'
+    assert tools[1].__class__.__name__ == 'DiscoveryEngineSearchTool'
+
+  @mock.patch(
+      'google.auth.default',
+      mock.MagicMock(return_value=('credentials', 'project')),
+  )
+  async def test_vais_no_bypass_custom_name_does_not_affect_builtin_name(self):
+    """name param has no effect on the built-in grounding tool name (bypass=False)."""
+    agent = LlmAgent(
+        name='test_agent',
+        model='gemini-pro',
+        tools=[
+            VertexAiSearchTool(
+                data_store_id='test_data_store_id',
+                bypass_multi_tools_limit=False,
+                name='should_be_ignored',
+            ),
+        ],
+    )
+    ctx = await _create_readonly_context(agent)
+    tools = await agent.canonical_tools(ctx)
+
+    assert len(tools) == 1
+    # The built-in grounding tool always reports 'vertex_ai_search'
+    assert tools[0].name == 'vertex_ai_search'
+    assert tools[0].__class__.__name__ == 'VertexAiSearchTool'
+
   async def test_handle_enterprise_web_search_in_hierarchy(self):
     """Enterprise web search without bypass remains a built-in search tool in a hierarchy."""
     search_agent = LlmAgent(

tests/unittests/tools/test_discovery_engine_search_tool.py

@@ -83,6 +83,38 @@ def test_init_with_data_store_specs_without_search_engine_id_raises_error(
           data_store_id="test_data_store", data_store_specs=[{"id": "123"}]
       )
 
+  def test_init_default_name(self):
+    """Default name is 'discovery_engine_search' (derived from the method name)."""
+    tool = DiscoveryEngineSearchTool(data_store_id="test_data_store")
+    assert tool.name == "discovery_engine_search"
+
+  def test_init_custom_name(self):
+    """Custom name overrides the default tool name."""
+    tool = DiscoveryEngineSearchTool(
+        data_store_id="test_data_store",
+        name="knowledge_base_search",
+    )
+    assert tool.name == "knowledge_base_search"
+
+  def test_init_custom_description(self):
+    """Custom description overrides the default tool description."""
+    custom_desc = "Search the internal product knowledge base."
+    tool = DiscoveryEngineSearchTool(
+        data_store_id="test_data_store",
+        description=custom_desc,
+    )
+    assert tool.description == custom_desc
+
+  def test_init_custom_name_and_description(self):
+    """Both custom name and description are applied simultaneously."""
+    tool = DiscoveryEngineSearchTool(
+        data_store_id="test_data_store",
+        name="product_search",
+        description="Search the product catalogue.",
+    )
+    assert tool.name == "product_search"
+    assert tool.description == "Search the product catalogue."
+
   @pytest.mark.parametrize(
       ("tool_kwargs", "expected_endpoint"),
       [