Python: Parse MCP CallToolResult.structuredContent field to prevent tool results returning None (#6421)

* Parse structuredContent from MCP CallToolResult (#3313)

The _parse_tool_result_from_mcp method only iterated over the content
field from CallToolResult, ignoring the structuredContent field entirely.
MCP servers that return JSON data via structuredContent (e.g., Power BI
MCP) appeared to return None.

Add handling for structuredContent: when present, serialize it as JSON
text and append it to the result list. This preserves the data for the
LLM while maintaining backward compatibility with existing behavior.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Python: Parse MCP CallToolResult.structuredContent field to prevent tool results returning None

Fixes #3313

* Address review feedback: add default=str to json.dumps and remove .checkpoints/

- Add default=str to json.dumps for structuredContent serialization so
  non-JSON-serializable values (e.g. bytes) degrade gracefully instead
  of raising TypeError
- Remove all .checkpoints/ runtime artifacts from the repository
- Add **/.checkpoints/ to .gitignore to prevent future accidental commits
- Add test for non-serializable structuredContent values

Fixes #3313

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Address review feedback for #3313: Python: MCP CallToolResult.structuredContent field is not parsed, causing tool results to return None

---------

Co-authored-by: Copilot <copilot@github.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

python/samples/02-agents/harness/console/agent_runner.py

@@ -313,9 +313,7 @@ class HarnessAgentRunner:
         """
         actions: list[FollowUpAction] = []
         for observer in self._observers:
-            observer_actions = await observer.on_stream_complete(
-                self._ux, self._agent, session
-            )
+            observer_actions = await observer.on_stream_complete(self._ux, self._agent, session)
             if observer_actions:
                 actions.extend(observer_actions)
         return actions

python/samples/02-agents/harness/console/app.py

@@ -182,18 +182,12 @@ class HarnessApp(App[None]):
         if command_handlers is None:
             from .commands import build_default_command_handlers
 
-            self._command_handlers = build_default_command_handlers(
-                agent, mode_colors=mode_colors
-            )
+            self._command_handlers = build_default_command_handlers(agent, mode_colors=mode_colors)
         else:
             self._command_handlers = command_handlers
 
         # Compute help text from command handlers
-        help_parts = [
-            h.get_help_text()
-            for h in self._command_handlers
-            if h.get_help_text() is not None
-        ]
+        help_parts = [h.get_help_text() for h in self._command_handlers if h.get_help_text() is not None]
         help_text = ", ".join(help_parts) if help_parts else None
 
         # State and driver

python/samples/02-agents/harness/console/commands/todo_handler.py

@@ -45,9 +45,7 @@ class TodoCommandHandler(CommandHandler):
             ux.append_info_line("TodoProvider is not available.")
             return True
 
-        todos = await self._todo_provider.store.load_items(
-            session, source_id=self._todo_provider.source_id
-        )
+        todos = await self._todo_provider.store.load_items(session, source_id=self._todo_provider.source_id)
 
         if not todos:
             ux.append_info_line("No todos yet.")

python/samples/02-agents/harness/console/components/scroll_panel.py

@@ -72,7 +72,7 @@ class HarnessScrollPanel(RichLog):
 
         # Truncate lines back to where streaming started
         if len(self.lines) > self._streaming_line_start:
-            del self.lines[self._streaming_line_start:]
+            del self.lines[self._streaming_line_start :]
             from textual.geometry import Size
 
             self.virtual_size = Size(self._widest_line_width, len(self.lines))

python/samples/02-agents/harness/console/observers/planning_models.py

@@ -41,8 +41,7 @@ class PlanningQuestion(BaseModel):
     choices: list[str] | None = Field(
         default=None,
         description=(
-            "For clarifications, this has a list of options that the user can "
-            "choose from. null for approvals."
+            "For clarifications, this has a list of options that the user can choose from. null for approvals."
         ),
     )