test: clarify sanitized tool error coverage

Author: uuzzrm

src/mcp/server/mcpserver/tools/base.py

@@ -184,5 +184,7 @@ async def run(
         except ToolError:
             raise
         except Exception:
+            # Intentional broad catch at the tool execution boundary: arbitrary
+            # tool exceptions must not cross the MCP boundary with their value.
             logger.exception("Error executing tool %s", self.name)
             raise ToolError(f"An unexpected error occurred while executing tool {self.name}") from None

tests/server/mcpserver/test_tool_manager.py

@@ -383,7 +383,7 @@ async def async_tool(x: int, ctx: Context) -> str:
         assert result == "42"
 
     @pytest.mark.anyio
-    async def test_context_error_handling(self):
+    async def test_context_error_handling(self) -> None:
         """Test error handling when context injection fails."""
 
         def tool_with_context(x: int, ctx: Context) -> str:
@@ -392,9 +392,11 @@ def tool_with_context(x: int, ctx: Context) -> str:
         manager = ToolManager()
         manager.add_tool(tool_with_context)
 
-        with pytest.raises(ToolError, match="^An unexpected error occurred while executing tool tool_with_context$"):
+        with pytest.raises(ToolError) as exc_info:
             await manager.call_tool("tool_with_context", {"x": 42}, context=Context())
 
+        assert str(exc_info.value) == "An unexpected error occurred while executing tool tool_with_context"
+
 
 class TestToolAnnotations:
     def test_tool_annotations(self):

tests/server/mcpserver/tools/test_base.py

@@ -43,12 +43,8 @@ async def needs_sampling() -> str:
 
 
 @pytest.mark.anyio
-async def test_non_mcperror_exception_raised_from_a_tool_is_wrapped_as_an_is_error_result():
-    """Unexpected tool exceptions become sanitized ``is_error`` results.
-
-    The original exception is logged server-side rather than returned to the client.
-    Pins the other arm of the same branch.
-    """
+async def test_non_mcperror_exception_raised_from_a_tool_is_wrapped_as_an_is_error_result() -> None:
+    """SDK-defined: unexpected tool exceptions become sanitized ``is_error`` results."""
     mcp = MCPServer(name="srv")
 
     @mcp.tool()
@@ -63,7 +59,8 @@ async def boom() -> str:
 
 
 @pytest.mark.anyio
-async def test_unexpected_tool_error_is_sanitized_and_logged(caplog: pytest.LogCaptureFixture):
+async def test_unexpected_tool_error_is_sanitized_and_logged(caplog: pytest.LogCaptureFixture) -> None:
+    """SDK-defined: ``Tool.run`` logs exception details but exposes a stable message."""
     secret = "database password"
 
     def boom() -> str:
@@ -81,11 +78,15 @@ def boom() -> str:
 
 
 @pytest.mark.anyio
-async def test_tool_error_is_re_raised_without_wrapping():
+async def test_tool_error_is_re_raised_without_wrapping() -> None:
+    """SDK-defined: an explicit ``ToolError`` remains actionable and is not wrapped."""
+
     def fail() -> str:
         raise ToolError("the requested record is unavailable")
 
     tool = Tool.from_function(fail)
 
-    with pytest.raises(ToolError, match="^the requested record is unavailable$"):
+    with pytest.raises(ToolError) as exc_info:
         await tool.run({}, Context())
+
+    assert str(exc_info.value) == "the requested record is unavailable"