fix: preserve static MCP meta in converted function tools (#2769)

Author: seratch

src/agents/mcp/util.py

@@ -177,6 +177,28 @@ def create_static_tool_filter(
 class MCPUtil:
     """Set of utilities for interop between MCP and Agents SDK tools."""
 
+    @staticmethod
+    def _extract_static_meta(tool: Any) -> dict[str, Any] | None:
+        meta = getattr(tool, "meta", None)
+        if isinstance(meta, dict):
+            return copy.deepcopy(meta)
+
+        model_extra = getattr(tool, "model_extra", None)
+        if isinstance(model_extra, dict):
+            extra_meta = model_extra.get("meta")
+            if isinstance(extra_meta, dict):
+                return copy.deepcopy(extra_meta)
+
+        model_dump = getattr(tool, "model_dump", None)
+        if callable(model_dump):
+            dumped = model_dump()
+            if isinstance(dumped, dict):
+                dumped_meta = dumped.get("meta")
+                if isinstance(dumped_meta, dict):
+                    return copy.deepcopy(dumped_meta)
+
+        return None
+
     @classmethod
     async def get_all_function_tools(
         cls,
@@ -251,7 +273,13 @@ def to_function_tool(
         policies. If the server uses a callable approval policy, approvals default
         to required to avoid bypassing dynamic checks.
         """
-        invoke_func_impl = functools.partial(cls.invoke_mcp_tool, server, tool)
+        static_meta = cls._extract_static_meta(tool)
+        invoke_func_impl = functools.partial(
+            cls.invoke_mcp_tool,
+            server,
+            tool,
+            meta=static_meta,
+        )
         effective_failure_error_function = server._get_failure_error_function(
             failure_error_function
         )

tests/mcp/test_mcp_util.py

@@ -149,6 +149,62 @@ def resolve_meta(context):
     assert args == {"foo": "bar"}
 
 
+@pytest.mark.asyncio
+async def test_to_function_tool_passes_static_mcp_meta():
+    server = FakeMCPServer()
+    tool = MCPTool(
+        name="test_tool_1",
+        inputSchema={},
+        _meta={"locale": "en", "extra": "value"},
+    )
+
+    function_tool = MCPUtil.to_function_tool(tool, server, convert_schemas_to_strict=False)
+    tool_context = ToolContext(
+        context=None,
+        tool_name="test_tool_1",
+        tool_call_id="test_call_static_meta",
+        tool_arguments="{}",
+    )
+
+    await function_tool.on_invoke_tool(tool_context, "{}")
+
+    assert server.tool_metas[-1] == {"locale": "en", "extra": "value"}
+
+
+@pytest.mark.asyncio
+async def test_to_function_tool_merges_static_mcp_meta_with_resolver():
+    captured: dict[str, Any] = {}
+
+    def resolve_meta(context):
+        captured["run_context"] = context.run_context
+        captured["server_name"] = context.server_name
+        captured["tool_name"] = context.tool_name
+        captured["arguments"] = context.arguments
+        return {"request_id": "req-123", "locale": "ja"}
+
+    server = FakeMCPServer(tool_meta_resolver=resolve_meta)
+    tool = MCPTool(
+        name="test_tool_1",
+        inputSchema={},
+        _meta={"locale": "en", "extra": "value"},
+    )
+
+    function_tool = MCPUtil.to_function_tool(tool, server, convert_schemas_to_strict=False)
+    tool_context = ToolContext(
+        context={"request_id": "req-123"},
+        tool_name="test_tool_1",
+        tool_call_id="test_call_static_meta_with_resolver",
+        tool_arguments="{}",
+    )
+
+    await function_tool.on_invoke_tool(tool_context, "{}")
+
+    assert server.tool_metas[-1] == {"request_id": "req-123", "locale": "en", "extra": "value"}
+    assert captured["server_name"] == server.name
+    assert captured["tool_name"] == "test_tool_1"
+    assert captured["arguments"] == {}
+
+
 @pytest.mark.asyncio
 async def test_mcp_invoke_bad_json_errors(caplog: pytest.LogCaptureFixture):
     caplog.set_level(logging.DEBUG)