[DOCS] Python subagent example uses incorrect pattern to detect tool_use blocks

Documentation Type

Incorrect/outdated documentation

Documentation Location

https://platform.claude.com/docs/en/agent-sdk/subagents#detecting-subagent-invocation

Section/Topic

"Detecting subagent invocation" section, Python code example

Current Documentation

The Python example uses this pattern to detect tool_use blocks:

if getattr(block, 'type', None) == 'tool_use' and block.name == 'Task':
print(f"Subagent invoked: {block.input.get('subagent_type')}")

What's Wrong or Missing?

The getattr(block, 'type', None) == 'tool_use' check will always fail because ToolUseBlock dataclasses in the Python SDK do not expose a type attribute.

Other Python examples in the documentation correctly use isinstance():

• todo-tracking.md: if isinstance(block, ToolUseBlock) and block.name == "TodoWrite":
• python.md: if isinstance(block, ToolUseBlock):

The subagents page is inconsistent with the rest of the Python SDK documentation.

Suggested Improvement

Before:

if getattr(block, 'type', None) == 'tool_use' and block.name == 'Task':

After:

if isinstance(block, ToolUseBlock) and block.name == 'Task':

This follows the Pythonic pattern used elsewhere in the SDK documentation and will actually work.

Impact

High - Prevents users from using a feature

Additional Context

Affected Pages:
| Page | Line(s) | Context |
|------|---------|---------|
| https://platform.claude.com/docs/en/agent-sdk/subagents | 294 | Python example for detecting subagent invocation |

Total scope: 1 page affected

Correct patterns for reference:
| Page | Line(s) | Pattern Used |
|------|---------|--------------|
| https://platform.claude.com/docs/en/agent-sdk/todo-tracking | 66, 160 | isinstance(block, ToolUseBlock) |
| https://platform.claude.com/docs/en/agent-sdk/python | 2063, 2101 | isinstance(block, ToolUseBlock) |