feat: Raises an error when there are duplicate tool names.

PiperOrigin-RevId: 758760508

Author: Annhiluc

google/genai/_extra_utils.py

@@ -116,6 +116,11 @@ def get_function_map(
       raise errors.UnsupportedFunctionError(
           'MCP tools are not supported in synchronous methods.'
       )
+    for tool_name, _ in mcp_to_genai_tool_adapters.items():
+      if function_map.get(tool_name):
+        raise ValueError(
+            f'Tool {tool_name} is already defined for the request.'
+        )
     function_map.update(mcp_to_genai_tool_adapters)
   return function_map
 
@@ -459,6 +464,11 @@ async def parse_config_for_mcp_tools(
           if genai_tool.function_declarations:
             for function_declaration in genai_tool.function_declarations:
               if function_declaration.name:
+                if mcp_to_genai_tool_adapters.get(function_declaration.name):
+                  raise ValueError(
+                      f'Tool {function_declaration.name} is already defined for'
+                      ' the request.'
+                  )
                 mcp_to_genai_tool_adapters[function_declaration.name] = (
                     mcp_to_genai_tool_adapter
                 )

google/genai/tests/afc/test_get_function_map.py

@@ -128,3 +128,49 @@ async def list_tools(self):
       config, mcp_to_genai_tool_adapters, is_caller_method_async=True
   )
   assert isinstance(result['tool'], McpToGenAiToolAdapter)
+
+
+@pytest.mark.asyncio
+async def test_duplicate_mcp_tool_raises_error():
+  if not _is_mcp_imported:
+    return
+
+  class MockMcpClientSession(McpClientSession):
+
+    def __init__(self):
+      self._read_stream = None
+      self._write_stream = None
+
+    async def list_tools(self):
+      return mcp_types.ListToolsResult(
+          tools=[
+              mcp_types.Tool(
+                  name='tool',
+                  description='tool-description',
+                  inputSchema={
+                      'type': 'OBJECT',
+                      'properties': {
+                          'key1': {
+                              'type': 'STRING',
+                          },
+                          'key2': {
+                              'type': 'NUMBER',
+                          },
+                      },
+                  },
+              )
+          ]
+      )
+
+  def tool():
+    pass
+
+  session = MockMcpClientSession()
+  config = GenerateContentConfig(tools=[tool, session])
+  mcp_to_genai_tool_adapters = {
+      'tool': McpToGenAiToolAdapter(session, [await session.list_tools()]),
+  }
+  with pytest.raises(ValueError):
+    get_function_map(
+        config, mcp_to_genai_tool_adapters, is_caller_method_async=True
+    )

google/genai/tests/models/test_generate_content_mcp.py

@@ -20,6 +20,7 @@
 
 try:
   from mcp import types as mcp_types
+  from mcp import ClientSession as McpClientSession
 except ImportError as e:
   import sys
 
@@ -64,3 +65,43 @@ async def test_mcp_tools_async(client):
           args={'location': 'Boston'},
       )
   ]
+
+
+@pytest.mark.asyncio
+async def test_mcp_tools_duplicate_tool_name_raises_error(client):
+  class MockMcpClientSession(McpClientSession):
+
+    def __init__(self):
+      self._read_stream = None
+      self._write_stream = None
+
+    async def list_tools(self):
+      return mcp_types.ListToolsResult(
+          tools=[
+              mcp_types.Tool(
+                  name='get_weather',
+                  description='Get the weather in a city.',
+                  inputSchema={
+                      'type': 'object',
+                      'properties': {'location': {'type': 'string'}},
+                  },
+              ),
+              mcp_types.Tool(
+                  name='get_weather',
+                  description='Different tool to get the weather.',
+                  inputSchema={
+                      'type': 'object',
+                      'properties': {'location': {'type': 'string'}},
+                  },
+              ),
+          ]
+      )
+
+  with pytest.raises(ValueError):
+    await client.aio.models.generate_content(
+        model='gemini-2.0-flash',
+        contents=t.t_contents(None, 'What is the weather in Boston?'),
+        config={
+            'tools': [MockMcpClientSession()],
+        },
+    )